Subj : Southern Ontario Weather To : All From : Northern Realms Date : Thu Sep 18 2025 15:35:00 FPCN11 CWTO 181930 Forecasts for Southern Ontario and the National Capital Region issued by Environment Canada at 3:30 p.m. EDT Thursday 18 September 2025 for tonight Friday and Friday night. The next scheduled forecast will be issued at 5:00 a.m. EDT Friday. City of Toronto. Tonight..Partly cloudy. Wind becoming north 20 km/h this evening. Low 13. Friday..Clearing. High 21. UV index 6 or high. Friday night..Clear. Wind becoming northeast 20 km/h after midnight. Low 9. Windsor - Leamington - Essex County. Tonight..Partly cloudy. Becoming cloudy after midnight. Low 17. Friday..A mix of sun and cloud. Wind becoming northeast 30 km/h in the afternoon. High 24. Humidex 29. UV index 6 or high. Friday night..Partly cloudy. Clearing before morning. Wind northeast 30 km/h becoming light near midnight. Low 13. Chatham-Kent - Rondeau Park. Tonight..Partly cloudy. Low 14. Friday..A mix of sun and cloud. High 24. Humidex 29. UV index 6 or high. Friday night..Partly cloudy. Wind becoming east 20 km/h before morning. Low 13. Sarnia - Petrolia - Western Lambton County. Tonight..Increasing cloudiness early this evening. Low 14. Friday..Mainly cloudy. Wind becoming north 30 km/h late in the morning. High 23. Humidex 26. UV index 6 or high. Friday night..Partly cloudy. Wind north 30 km/h becoming light in the evening. Wind becoming east 20 before morning. Low 11. Watford - Pinery Park - Eastern Lambton County. Tonight..Partly cloudy. Low 14. Friday..Mainly cloudy. Clearing early in the afternoon. Wind northeast 20 km/h becoming light late in the morning. High 23. Humidex 26. UV index 6 or high. Friday night..Clear. Low 11. Rodney - Shedden - Western Elgin County. Tonight..Partly cloudy. Low 13. Friday..Mainly cloudy. High 23. Humidex 26. UV index 6 or high. Friday night..Partly cloudy. Low 12. St. Thomas - Aylmer - Eastern Elgin County. Tonight..A few clouds. Low 13. Friday..Mainly cloudy. High 23. Humidex 26. UV index 6 or high. Friday night..A few clouds. Wind becoming east 20 km/h before morning. Low 12. Strathroy - Komoka - Western Middlesex County. Tonight..Partly cloudy. Low 12. Friday..A mix of sun and cloud. High 23. Humidex 26. UV index 6 or high. Friday night..Partly cloudy. Low 11. London - Parkhill - Eastern Middlesex County. Tonight..A few clouds. Wind northwest 20 km/h becoming light early this evening. Low 12. Friday..A mix of sun and cloud. High 23. Humidex 26. UV index 6 or high. Friday night..Clear. Low 11. Simcoe - Delhi - Norfolk. Tonight..A few clouds. Wind west 20 km/h becoming light early this evening. Low 12. Friday..A mix of sun and cloud. High 22. UV index 6 or high. Friday night..Clear. Low 9. Dunnville - Caledonia - Haldimand. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 13. Friday..Mainly cloudy. Clearing early in the afternoon. High 22. UV index 6 or high. Friday night..Clear. Low 10. Woodstock - Tillsonburg - Oxford County. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 12. Friday..Clearing in the morning. High 23. UV index 6 or high. Friday night..Clear. Low 9. Brantford - County of Brant. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 12. Friday..A mix of sun and cloud. Clearing near noon. High 23. UV index 6 or high. Friday night..Clear. Low 9. Niagara Falls - Welland - Southern Niagara Region. Tonight..Partly cloudy. Becoming cloudy after midnight. Low 14. Friday..Cloudy. Clearing early in the afternoon. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 13. St. Catharines - Grimsby - Northern Niagara Region. Tonight..Partly cloudy. Wind west 20 km/h becoming light early this evening. Low 14. Friday..Mainly cloudy. Clearing early in the afternoon. High 21. UV index 6 or high. Friday night..Clear. Low 10. City of Hamilton. Tonight..Partly cloudy. Wind west 20 km/h becoming light early this evening. Low 13. Friday..Mainly cloudy. Clearing near noon. High 21. UV index 6 or high. Friday night..Clear. Low 10. Burlington - Oakville. Tonight..Partly cloudy. Low 13. Friday..Mainly cloudy. Clearing late in the morning. High 21. UV index 6 or high. Friday night..Clear. Wind becoming east 20 km/h gusting to 40 before morning. Low 9. Halton Hills - Milton. Tonight..Partly cloudy. Wind northwest 20 km/h gusting to 40 becoming northeast 20 then light this evening. Low 13. Friday..Clearing. High 21. UV index 6 or high. Friday night..Clear. Low 9. Mississauga - Brampton. Tonight..Partly cloudy. Low 13. Friday..Clearing. High 21. UV index 6 or high. Friday night..Clear. Low 9. Caledon. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h. Low 11. Friday..Clearing in the morning. High 20. UV index 6 or high. Friday night..Clear. Low 7. Vaughan - Richmond Hill - Markham. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 11. Friday..Clearing in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 8. Newmarket - Georgina - Northern York Region. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light late this evening. Low 10. Friday..Clearing in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 8. Pickering - Oshawa - Southern Durham Region. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 11. Friday..Clearing in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Uxbridge - Beaverton - Northern Durham Region. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 10. Friday..Clearing in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 8. Goderich - Bluewater - Southern Huron County. Tonight..Mainly cloudy. Wind north 20 km/h becoming light this evening. Low 10. Friday..Clearing. Wind becoming northeast 20 km/h late in the afternoon. High 22. UV index 6 or high. Friday night..Clear. Wind east 20 km/h. Low 7. Wingham - Blyth - Northern Huron County. Tonight..Mainly cloudy. Fog patches developing overnight. Wind northwest 20 km/h becoming light early this evening. Low 10. Friday..Clearing in the morning. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 7. Stratford - Mitchell - Southern Perth County. Tonight..Partly cloudy. Fog patches developing overnight. Wind northwest 20 km/h becoming light this evening. Low 9. Friday..Clearing. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 7. Listowel - Milverton - Northern Perth County. Tonight..Partly cloudy. Fog patches developing overnight. Wind northwest 20 km/h becoming light early this evening. Low 9. Friday..Clearing. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 7. Kitchener - Cambridge - Region of Waterloo. Tonight..Partly cloudy. Fog patches developing overnight. Wind northwest 20 km/h becoming light this evening. Low 10. Friday..Clearing. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 8. Guelph - Erin - Southern Wellington County. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Fog patches developing overnight. Wind northwest 20 km/h becoming light this evening. Low 10. Friday..Clearing. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 8. Mount Forest - Arthur - Northern Wellington County. Tonight..Partly cloudy. Becoming cloudy near midnight. Fog patches developing overnight. Wind northwest 20 km/h becoming light early this evening. Low 9. Friday..Clearing in the morning. Fog patches dissipating in the morning. High 22. UV index 6 or high. Friday night..Clear. Low 8. Orangeville - Grand Valley - Southern Dufferin County. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h becoming light after midnight. Low 9. Friday..Clearing in the morning. High 20. UV index 6 or high. Friday night..Clear. Low 6. Shelburne - Mansfield - Northern Dufferin County. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h becoming northeast 20 late this evening. Low 9. Friday..Clearing in the morning. High 20. UV index 6 or high. Friday night..Clear. Low 6. Innisfil - New Tecumseth - Angus. Tonight..Mainly cloudy. Wind northwest 20 km/h becoming light this evening. Low 9. Friday..Clearing in the morning. High 20. UV index 6 or high. Friday night..Clear. Low 6. Saugeen Shores - Kincardine - Southern Bruce County. Tonight..Mainly cloudy. Fog patches developing overnight. Low 9. Friday..Clearing in the morning. Fog patches dissipating in the morning. High 20. UV index 6 or high. Friday night..Clear. Low 10. Bruce Peninsula - Sauble Beach - Tobermory. Tonight..Mainly cloudy. Wind becoming northeast 20 km/h gusting to 40 this evening. Low 9. Friday..A mix of sun and cloud. Clearing near noon. Wind northeast 20 km/h. High 18. UV index 6 or high. Friday night..Clear. Low 7. Hanover - Dundalk - Southern Grey County. Tonight..Partly cloudy. Becoming cloudy late this evening. Fog patches developing overnight. Wind becoming northeast 20 km/h late this evening. Low 9. Friday..Clearing. Fog patches dissipating in the morning. High 19. UV index 6 or high. Friday night..Clear. Low 7. Owen Sound - Blue Mountains - Northern Grey County. Tonight..Mainly cloudy. Wind becoming northeast 20 km/h this evening. Low 9. Friday..A mix of sun and cloud. Clearing near noon. Wind northeast 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low 7. Barrie - Collingwood - Hillsdale. Tonight..Mainly cloudy. Wind northwest 20 km/h becoming light this evening. Low 9. Friday..Mainly sunny. High 19. UV index 6 or high. Friday night..Clear. Wind becoming east 20 km/h before morning. Low 7. Midland - Coldwater - Orr Lake. Tonight..Mainly cloudy. Wind northwest 30 km/h. Low 9. Friday..A mix of sun and cloud. Becoming sunny in the morning. High 19. UV index 6 or high. Friday night..Clear. Wind northeast 20 km/h. Low 7. Orillia - Lagoon City - Washago. Tonight..Partly cloudy. Wind northwest 30 km/h becoming light late this evening. Low 9. Friday..Sunny. High 19. UV index 6 or high. Friday night..Clear. Wind becoming east 30 km/h near midnight. Low 7. Cobourg - Colborne - Western Northumberland County. Tonight..Partly cloudy. Wind west 20 km/h becoming light early this evening. Low 11. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Belleville - Quinte West - Eastern Northumberland County. Tonight..Partly cloudy. Wind west 20 km/h becoming light early this evening. Low 11. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Picton - Sandbanks Park. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind west 20 km/h becoming light early this evening. Low 10. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Napanee - Consecon. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind west 20 km/h becoming light early this evening. Low 10. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Kingston - Odessa - Frontenac Islands. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind southwest 30 km/h becoming light early this evening. Low 10. Friday..Clearing in the morning. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low 7. Lindsay - Southern Kawartha Lakes. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light early this evening. Low 8. Friday..Sunny. High 21. UV index 6 or high. Friday night..Clear. Low plus 4. Fenelon Falls - Balsam Lake Park - Northern Kawartha Lakes. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 6. Friday..Sunny. High 21. UV index 6 or high. Friday night..Clear. Low plus 4. Peterborough City - Lakefield - Southern Peterborough County. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light this evening. Low 8. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low plus 4. Apsley - Woodview - Northern Peterborough County. Tonight..Partly cloudy. Wind northwest 20 km/h becoming light early this evening. Low 6. Friday..A mix of sun and cloud. Becoming sunny in the morning. Wind north 20 km/h becoming light late in the morning. High 21. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. Stirling - Tweed - Madoc. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h becoming light early this evening. Low 8. Friday..Sunny. Wind north 20 km/h becoming light late in the morning. High 20. UV index 6 or high. Friday night..Clear. Low plus 5. Tamworth - Sydenham - South Frontenac. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h. Low 8. Friday..Mainly sunny. Wind north 20 km/h becoming light late in the morning. High 20. UV index 6 or high. Friday night..Clear. Low plus 5. Kaladar - Bannockburn - Bon Echo Park. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h becoming light late this evening. Low 6. Friday..A mix of sun and cloud. Becoming sunny in the morning. Wind north 20 km/h becoming light late in the morning. High 20. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. Bancroft - Hastings Highlands - Denbigh. Tonight..Cloudy. Becoming partly cloudy this evening. Wind north 20 km/h becoming light late this evening. Low plus 4. Friday..Clearing. Wind north 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 1 with frost. Gananoque - Mallorytown. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind becoming north 20 km/h before morning. Low 9. Friday..A mix of sun and cloud. Becoming sunny near noon. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Brockville - Prescott. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Low 9. Friday..A mix of sun and cloud. Clearing early in the afternoon. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Westport - Charleston Lake. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h becoming light late this evening. Low 9. Friday..A mix of sun and cloud. Clearing near noon. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Merrickville-Wolford - Kemptville. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h. Low 9. Friday..A mix of sun and cloud. Becoming sunny in the afternoon. Wind north 20 km/h. High 19. UV index 6 or high. Friday night..Clear. Wind north 20 km/h becoming light in the evening. Low plus 4. Ottawa North - Kanata - Orleans. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind north 30 km/h becoming light early this evening. Low 9. Friday..Mainly sunny. Wind north 20 km/h. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Ottawa South - Richmond - Metcalfe. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind north 30 km/h becoming light early this evening. Low 9. Friday..Mainly sunny. Wind north 20 km/h. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Gatineau. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Clearing overnight. Wind northwest 20 km/h becoming light early this evening. Low 8. Friday..Sunny. Wind becoming northwest 20 km/h in the morning. High 19. UV index 6 or high. Friday night..Clear. Wind northwest 20 km/h becoming light in the evening. Low plus 4. Prescott and Russell. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Low 7. Friday..Mainly sunny. Wind north 20 km/h. High 19. UV index 6 or high. Friday night..Clear. Wind north 20 km/h becoming light in the evening. Low plus 4. Morrisburg - Long Sault. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h becoming light this evening. Low 8. Friday..A mix of sun and cloud. Clearing early in the afternoon. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Cornwall - Lancaster. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 30 km/h becoming light this evening. Low 8. Friday..Mainly cloudy. Clearing early in the afternoon. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Winchester - Newington. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h gusting to 40 becoming light this evening. Low 8. Friday..A mix of sun and cloud. Becoming sunny in the afternoon. Wind north 20 km/h becoming light in the afternoon. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Maxville - Alexandria. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h gusting to 40 becoming light this evening. Low 8. Friday..Mainly sunny. Wind north 20 km/h becoming light in the afternoon. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Plevna - Sharbot Lake - Western Lanark County. Tonight..Partly cloudy. 30 percent chance of showers early this evening. Wind north 20 km/h becoming light late this evening. Low 8. Friday..A mix of sun and cloud. Clearing late in the morning. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. Smiths Falls - Perth - Eastern Lanark County. Tonight..Mainly cloudy. 30 percent chance of showers early this evening. Wind northwest 20 km/h becoming light this evening. Low 8. Friday..A mix of sun and cloud. Becoming sunny in the afternoon. Wind north 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Port Carling - Port Severn. Tonight..Mainly cloudy. Clearing after midnight. Wind northwest 30 km/h becoming light late this evening. Wind becoming north 20 after midnight. Low 7. Friday..A mix of sun and cloud. Becoming sunny in the morning. High 19. UV index 6 or high. Friday night..Clear. Wind becoming east 20 km/h before morning. Low plus 4. Bracebridge - Gravenhurst. Tonight..Mainly cloudy. Clearing after midnight. Low plus 5. Friday..Clearing in the morning. High 19. UV index 6 or high. Friday night..Clear. Low plus 4. Town of Parry Sound - Rosseau - Killbear Park. Tonight..Mainly cloudy. Clearing near midnight. Wind becoming north 30 km/h early this evening then light late this evening. Low 6. Friday..Clearing. Wind northeast 20 km/h becoming light late in the morning. High 19. UV index 6 or high. Friday night..Clear. Wind becoming east 20 km/h before morning. Low plus 5. Huntsville - Baysville. Tonight..Cloudy. Becoming partly cloudy near midnight. Low plus 3. Friday..Clearing. High 17. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. Haliburton - Minden - Southern Haliburton County. Tonight..Cloudy. Becoming partly cloudy this evening. Wind north 20 km/h becoming light this evening. Low plus 4. Friday..Clearing. Wind north 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 1 with risk of frost. Oxtongue Lake - Fort Irwin - Northern Haliburton County. Tonight..Cloudy. Becoming partly cloudy this evening. Low plus 3 with risk of frost. Friday..Clearing. Wind north 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 1 with risk of frost. Barry's Bay - Killaloe. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind north 20 km/h becoming light after midnight. Low plus 4. Friday..A mix of sun and cloud. Clearing late in the morning. Wind becoming north 20 km/h in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 1 with risk of frost. Renfrew - Arnprior - Calabogie. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind north 20 km/h gusting to 40 becoming light after midnight. Low 7. Friday..A mix of sun and cloud. Clearing late in the morning. Wind north 20 km/h. High 18. UV index 6 or high. Friday night..Clear. Low plus 2 with risk of frost. Petawawa - Pembroke - Cobden. Tonight..Cloudy. Becoming partly cloudy late this evening. Wind north 30 km/h gusting to 50. Low plus 5. Friday..A mix of sun and cloud. Becoming sunny in the morning. Wind north 30 km/h. High 18. UV index 6 or high. Friday night..Clear. Wind north 30 km/h becoming light after midnight. Low plus 2 with risk of frost. Western Algonquin Park - Lake of Two Rivers. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind becoming north 30 km/h early this evening then light after midnight. Low plus 3 with risk of frost. Friday..Mainly cloudy. Clearing late in the morning. Wind north 20 km/h. High 16. UV index 6 or high. Friday night..Clear. Low zero with patchy frost. Deep River - Whitney - Eastern Algonquin Park. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind north 20 km/h becoming light this evening. Low plus 3 with risk of frost. Friday..Mainly cloudy. Clearing late in the morning. Wind north 20 km/h becoming light late in the morning. High 16. UV index 6 or high. Friday night..Clear. Low zero with patchy frost. Bayfield Inlet - Dunchurch. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind north 20 km/h becoming light after midnight. Low plus 5. Friday..Clearing. Wind north 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. South River - Burk's Falls. Tonight..Cloudy. Becoming partly cloudy near midnight. Wind north 20 km/h becoming light after midnight. Low plus 4. Friday..Clearing. Wind north 20 km/h becoming light late in the morning. High 18. UV index 6 or high. Friday night..Clear. Low plus 3 with risk of frost. End $$$$^^ --- up 1 day, 23 hours, 27 minutes * Origin: Northern Realms (618:400/23) .