Sarnia weather
Loading live data…Heavy drizzle,rain likely tomorrow
Env. Canada, the European and the American model put Sarnia's high today between 17° and 23°, a 6° split. Tomorrow looks light drizzle around 19°, with a 90% chance of rain.
CheckWeather.io on iPhoneFree. No ads, no account.Sarnia weather in numbers
measured normals and 10 years of recorded weatherSarnia swings 30°C across the year, from 26°C highs in July to -4°C lows in January, and August is usually the wettest month in a year that brings about 970 mm of precipitation. Over 10 years of recorded weather it averages 68 days a year at 25°C or above, 15 of them at 30°C or above, 116 frost nights, and rain on 134 days.
Day counts are from the ERA5 reanalysis for Sarnia’s grid square, 2016 to 2025, counted the same way for every city so the numbers compare. A reanalysis square is an area, not a weather station, so it is good for counting days and not for a single day’s record.
The weather map: all three models at once
Env. Canada, European, American side by side around Sarnia and nearby towns.Live rain radar →Sarnia hourly forecast: next 14 hours
consensus of the three modelsRain in the next 24 hours, model by model
each model's own hourly precipitation, side by sideLoading the three models…
Sarnia 10-day forecast, out to 14 days
where the models agree, and where they splitSarnia, Ontario is at its warmest in Jul (average highs near 26°C) and coldest in Jan (lows around -4°C), with roughly 970 mm of precipitation across the year. Below, compare what Env. Canada, European, American forecast for Sarnia right now, and see exactly where they disagree.
We grade every model against the weather that actually happened, so you can see which forecast model is most accurate in Canada before you trust any single number.
Sarnia climate by month
average daytime high and overnight low across a typical yearWhich forecast is most accurate in Sarnia?
CheckWeather Score, graded against the weather that actually happened
The CheckWeather Score blends temperature, wind and rain accuracy, each measured against ERA5 (the recorded weather) over the last 30 days across 1304 cities. Lower error means a higher score. See which forecast model is most accurate in Canada, how we measure forecast accuracy, or which model each weather app uses.
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your vote countsThe accuracy above is the measured record. This is your opinion: which forecast service do you trust most in Canada? Give each 1 to 5 stars.
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Where the models disagree
temperature and rain, judged separatelyThe models often agree on temperature and still split on rain, and rain is usually what decides whether a plan survives. A wide rain range means the shower is genuinely uncertain, not that the forecast is wrong.