Subj : Southern Ontario Weather To : All From : Northern Realms Date : Thu Aug 21 2025 15:35:00 FPCN11 CWTO 211930 Forecasts for Southern Ontario and the National Capital Region issued by Environment Canada at 3:30 p.m. EDT Thursday 21 August 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..Clear. Low 15. Friday..Sunny. High 27. Humidex 30. UV index 8 or very high. Friday night..Clear. Low 17. Windsor - Leamington - Essex County. Tonight..Clearing early this evening. Fog patches developing near midnight. Wind northeast 20 km/h becoming light this evening. Low 15. Friday..Sunny. Fog patches dissipating in the morning. High 27. Humidex 30. UV index 9 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Fog patches developing after midnight. Low 16. Chatham-Kent - Rondeau Park. Tonight..Clear. Fog patches developing near midnight. Wind northeast 20 km/h becoming light early this evening. Low 15. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 9 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Fog patches developing after midnight. Low 15. Sarnia - Petrolia - Western Lambton County. Tonight..Clear. Fog patches developing near midnight. Wind north 20 km/h becoming light this evening. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 31. UV index 9 or very high. Friday night..Clear. Increasing cloudiness before morning. Fog patches developing after midnight. Low 16. Watford - Pinery Park - Eastern Lambton County. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 31. UV index 9 or very high. Friday night..Clear. Increasing cloudiness before morning. Fog patches developing after midnight. Low 16. Rodney - Shedden - Western Elgin County. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 25. Humidex 30. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 16. St. Thomas - Aylmer - Eastern Elgin County. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 25. Humidex 30. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 16. Strathroy - Komoka - Western Middlesex County. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 31. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 16. London - Parkhill - Eastern Middlesex County. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 31. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 16. Simcoe - Delhi - Norfolk. Tonight..Partly cloudy. Becoming clear this evening. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 15. Dunnville - Caledonia - Haldimand. Tonight..Clearing early this evening. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 25. Humidex 28. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 14. Woodstock - Tillsonburg - Oxford County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 14. Brantford - County of Brant. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 9 or very high. Friday night..Clear. Fog patches developing after midnight. Low 14. Niagara Falls - Welland - Southern Niagara Region. Tonight..Partly cloudy. Clearing this evening. Low 14. Friday..Sunny. High 27. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. St. Catharines - Grimsby - Northern Niagara Region. Tonight..Partly cloudy. Clearing this evening. Wind northeast 20 km/h becoming light this evening. Low 14. Friday..Sunny. High 27. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. City of Hamilton. Tonight..Clear. Wind northeast 20 km/h becoming light this evening. Low 13. Friday..Sunny. High 25. Humidex 28. UV index 9 or very high. Friday night..Clear. Low 14. Burlington - Oakville. Tonight..Clear. Wind northeast 30 km/h becoming light this evening. Low 14. Friday..Sunny. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 14. Halton Hills - Milton. Tonight..Clear. Low 14. Friday..Sunny. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 14. Mississauga - Brampton. Tonight..Clear. Low 14. Friday..Sunny. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. Caledon. Tonight..Clear. Fog patches developing near midnight. Low 14. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 17. Vaughan - Richmond Hill - Markham. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. Newmarket - Georgina - Northern York Region. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. Pickering - Oshawa - Southern Durham Region. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 17. Uxbridge - Beaverton - Northern Durham Region. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 16. Goderich - Bluewater - Southern Huron County. Tonight..Clear. Fog patches developing near midnight. Wind east 20 km/h becoming light early this evening. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness before morning. Low 16. Wingham - Blyth - Northern Huron County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness before morning. Low 16. Stratford - Mitchell - Southern Perth County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness before morning. Low 16. Listowel - Milverton - Northern Perth County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness before morning. Low 16. Kitchener - Cambridge - Region of Waterloo. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 9 or very high. Friday night..Clear. Increasing cloudiness before morning. Low 14. Guelph - Erin - Southern Wellington County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 9 or very high. Friday night..Clear. Increasing cloudiness before morning. Low 14. Mount Forest - Arthur - Northern Wellington County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 25. Humidex 29. UV index 9 or very high. Friday night..Clear. Increasing cloudiness before morning. Low 17. Orangeville - Grand Valley - Southern Dufferin County. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 17. Shelburne - Mansfield - Northern Dufferin County. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 17. Innisfil - New Tecumseth - Angus. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 9 or very high. Friday night..Clear. Low 17. Saugeen Shores - Kincardine - Southern Bruce County. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness after midnight. Low 18 with temperature rising to 21 by morning. Bruce Peninsula - Sauble Beach - Tobermory. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness after midnight. Low 18. Hanover - Dundalk - Southern Grey County. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 25. Humidex 29. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness after midnight. Low 17. Owen Sound - Blue Mountains - Northern Grey County. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..A few clouds. Increasing cloudiness after midnight. Low 18. Barrie - Collingwood - Hillsdale. Tonight..Clear. Fog patches developing near midnight. Low 12. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 31. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 17. Midland - Coldwater - Orr Lake. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 31. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 17. Orillia - Lagoon City - Washago. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 31. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 20. Cobourg - Colborne - Western Northumberland County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 15. Belleville - Quinte West - Eastern Northumberland County. Tonight..Clear. Fog patches developing near midnight. Low 13. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 15. Picton - Sandbanks Park. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 15. Napanee - Consecon. Tonight..Clear. Low 12. Friday..Sunny. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 15. Kingston - Odessa - Frontenac Islands. Tonight..Clear. Low 12. Friday..Sunny. High 27. Humidex 30. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 17. Lindsay - Southern Kawartha Lakes. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 15. Fenelon Falls - Balsam Lake Park - Northern Kawartha Lakes. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 14. Peterborough City - Lakefield - Southern Peterborough County. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Low 14. Apsley - Woodview - Northern Peterborough County. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 30. UV index 8 or very high. Friday night..A few clouds. Low 13. Stirling - Tweed - Madoc. Tonight..Clear. Low 12. Friday..Sunny. High 27. Humidex 29. UV index 8 or very high. Friday night..Clear. Low 15. Tamworth - Sydenham - South Frontenac. Tonight..Clear. Low 12. Friday..Sunny. High 27. Humidex 29. UV index 8 or very high. Friday night..Clear. Low 15. Kaladar - Bannockburn - Bon Echo Park. Tonight..Clear. Low 9. Friday..Sunny. High 27. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness before morning. Low 14. Bancroft - Hastings Highlands - Denbigh. Tonight..Clear. Low 9. Friday..Sunny. High 27. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness before morning. Low 13. Gananoque - Mallorytown. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 9 or very high. Friday night..Clear. Low 16. Brockville - Prescott. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 9 or very high. Friday night..Clear. Low 16. Westport - Charleston Lake. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 9 or very high. Friday night..Clear. Low 16. Merrickville-Wolford - Kemptville. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 9 or very high. Friday night..Clear. Low 16. Ottawa North - Kanata - Orleans. Tonight..Clear. Low 13. Friday..Sunny. High 28. Humidex 30. UV index 8 or very high. Friday night..Clear. Low 16. Ottawa South - Richmond - Metcalfe. Tonight..Clear. Low 13. Friday..Sunny. High 28. Humidex 30. UV index 8 or very high. Friday night..Clear. Low 16. Gatineau. Tonight..Clear. Low 13. Friday..Sunny. High 28. Humidex 30. UV index 8 or very high. Friday night..Clear. Low 16. Prescott and Russell. Tonight..Clear. Low 12. Friday..Sunny. High 28. Humidex 30. UV index 8 or very high. Friday night..Clear. Low 16. Morrisburg - Long Sault. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..Clear. Low 17. Cornwall - Lancaster. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..Clear. Low 17. Winchester - Newington. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..Clear. Low 17. Maxville - Alexandria. Tonight..Clear. Low 11. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..Clear. Low 16. Plevna - Sharbot Lake - Western Lanark County. Tonight..Clear. Low 12. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..A few clouds. Low 16. Smiths Falls - Perth - Eastern Lanark County. Tonight..Clear. Low 12. Friday..Sunny. High 28. Humidex 31. UV index 8 or very high. Friday night..A few clouds. Low 17. Port Carling - Port Severn. Tonight..Clear. Low 15. Friday..Sunny. High 25. Humidex 30. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 17. Bracebridge - Gravenhurst. Tonight..Clear. Low 10. Friday..Sunny. High 26. Humidex 31. UV index 8 or very high. Friday night..Clear. Becoming partly cloudy after midnight. Low 17. Town of Parry Sound - Rosseau - Killbear Park. Tonight..Clear. Low 12. Friday..Sunny. High 25. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 17. Huntsville - Baysville. Tonight..Clear. Low 10. Friday..Sunny. High 25. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 17. Haliburton - Minden - Southern Haliburton County. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 13. Oxtongue Lake - Fort Irwin - Northern Haliburton County. Tonight..Clear. Fog patches developing near midnight. Low 10. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 12. Barry's Bay - Killaloe. Tonight..Clear. Low 12. Friday..Mainly sunny. High 27. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 18. Renfrew - Arnprior - Calabogie. Tonight..Clear. Low 12. Friday..Mainly sunny. High 27. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 18. Petawawa - Pembroke - Cobden. Tonight..Clear. Low 12. Friday..Mainly sunny. High 27. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 18. Western Algonquin Park - Lake of Two Rivers. Tonight..Clear. Low 9. Friday..Sunny. High 25. Humidex 28. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 14. Deep River - Whitney - Eastern Algonquin Park. Tonight..Clear. Fog patches developing near midnight. Low 9. Friday..Sunny. Fog patches dissipating in the morning. High 26. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 15. Bayfield Inlet - Dunchurch. Tonight..Clear. Low 11. Friday..Sunny. High 25. Humidex 29. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 17. South River - Burk's Falls. Tonight..Clear. Low 10. Friday..Sunny. High 26. Humidex 30. UV index 8 or very high. Friday night..Clear. Increasing cloudiness after midnight. Low 15. End $$$$^^ --- up 11 hours, 58 minutes * Origin: Northern Realms (618:400/23) .