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SunnyDays

ERA5 almanac — 8 years of real data

Toronto in September

Toronto in September: 30% of days see measurable rain, 72°F average high, 25% of days historically clear (n=240, ERA5 2018–2025).

Toronto in September is historically a poor month for sun: only 25% of days clear across 8 years (n=240, avg high 72°F). August is the clearest month for Toronto historically. Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Toronto page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late September

Clear-sky percentage for Toronto in September, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early September
1st–15th		 27% n=120 72°F
Late September
16th–end		 23% n=120 72°F
Full month average 25% n=240 72°F

Sunshine & warmth in September

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Toronto in September. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early September
1st–15th		 58% n=120
Late September
16th–end		 39% n=120
Full month average 48% n=240
11.4 h median sunshine per day 78% of days exceed 8 h sunshine 30% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 25%. Sunshine-based “warm & sunny”: 48%. The 23-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Toronto is mostly overcast in September historically: only 25% of days are clear across 8 years (n=240), avg high 72°F. If you want sun in Toronto, August is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in August — historically the best month for sun in Toronto.

Every month in Toronto

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Toronto, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 0% n=248 All destinations →
April 1% n=240 All destinations →
May 13% n=248 All destinations →
June 30% n=240 All destinations →
July 34% n=248 All destinations →
August 36% n=248 All destinations →
September ← this page 25% n=240 All destinations →
October 5% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Toronto in September?

Sometimes. Toronto sees measurable rain on 30% of days in September historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Toronto good for sun in September?

Not usually. Toronto is historically overcast in September: only 25% of days are clear (avg high 72°F, n=240 days, ERA5 2018–2025). August is historically far better for sun here.

How Toronto compares in September

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Toronto this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.