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SunnyDays

ERA5 almanac — 8 years of real data

Tulum in May

Tulum in May: 51% of days see measurable rain, 87°F average high, 16% of days historically clear (n=248, ERA5 2018–2025).

Tulum in May is historically a poor month for sun: only 16% of days clear across 8 years (n=248, avg high 87°F). April is the clearest month for Tulum 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 Tulum 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 Tulum 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		 24% n=120 87°F
Late May
16th–end		 9% n=128 87°F
Full month average 16% n=248 87°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 Tulum 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		 100% n=120
Late May
16th–end		 95% n=128
Full month average 97% n=248
12.3 h median sunshine per day 95% of days exceed 8 h sunshine 51% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 16%. Sunshine-based “warm & sunny”: 97%. The 81-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

Tulum is a poor choice for sun in May: just 16% of days clear historically (n=248). April 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 April — historically the best month for sun in Tulum.

Every month in Tulum

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

Historical clear-sky % for Tulum, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 23% n=248 All destinations →
February 23% n=226 All destinations →
March 28% n=248 All destinations →
April 30% n=240 All destinations →
May ← this page 16% n=248 All destinations →
June 6% n=240 All destinations →
July 11% n=248 All destinations →
August 8% n=248 All destinations →
September 4% n=240 All destinations →
October 11% n=248 All destinations →
November 20% n=240 All destinations →
December 21% n=248 All destinations →

Frequently asked

Does it rain in Tulum in May?

Yes, frequently. In Tulum, 51% of days in May see measurable rain, based on 8 years of ERA5 historical data (n=248 days, 2018–2025). This is a historical average, not a forecast.

Is Tulum good for sun in May?

Not usually. Tulum is historically overcast in May: only 16% of days are clear (avg high 87°F, n=248 days, ERA5 2018–2025). April is historically far better for sun here.

How Tulum compares in May

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