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SunnyDays

ERA5 almanac — 8 years of real data

Montréal in May

Montréal in May: 35% of days see measurable rain, 67°F average high, 17% of days historically clear (n=248, ERA5 2018–2025).

Montréal in May is historically a poor month for sun: only 17% of days clear across 8 years (n=248, avg high 67°F). July is the clearest month for Montréal 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 Montréal 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 May

Clear-sky percentage for Montréal in May, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early May
1st–15th		 9% n=120 67°F
Late May
16th–end		 24% n=128 67°F
Full month average 17% n=248 67°F

Sunshine & warmth in May

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 Montréal in May. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early May
1st–15th		 13% n=120
Late May
16th–end		 43% n=128
Full month average 28% n=248
12.0 h median sunshine per day 73% of days exceed 8 h sunshine 35% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 17%. Sunshine-based “warm & sunny”: 28%. The 11-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

Montréal is a poor choice for sun in May: just 17% of days clear historically (n=248). July is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in July — historically the best month for sun in Montréal.

Every month in Montréal

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

Historical clear-sky % for Montréal, 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 2% n=240 All destinations →
May ← this page 17% n=248 All destinations →
June 31% n=240 All destinations →
July 35% n=248 All destinations →
August 31% n=248 All destinations →
September 22% n=240 All destinations →
October 4% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Montréal in May?

Sometimes. Montréal sees measurable rain on 35% of days in May historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Montréal good for sun in May?

Not usually. Montréal is historically overcast in May: only 17% of days are clear (avg high 67°F, n=248 days, ERA5 2018–2025). July is historically far better for sun here.

How Montréal compares in May

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Montréal 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.