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SunnyDays

ERA5 almanac — 8 years of real data

Bangkok in May

Bangkok in May: 70% of days see measurable rain, 92°F average high, 10% of days historically clear (n=248, ERA5 2018–2025).

Bangkok in May is historically a poor month for sun: only 10% of days clear across 8 years (n=248, avg high 92°F). January is the clearest month for Bangkok 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 Bangkok 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 Bangkok 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		 13% n=120 92°F
Late May
16th–end		 8% n=128 92°F
Full month average 10% n=248 92°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 Bangkok 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		 93% n=120
Late May
16th–end		 93% n=128
Full month average 93% n=248
10.6 h median sunshine per day 81% of days exceed 8 h sunshine 70% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 10%. Sunshine-based “warm & sunny”: 93%. The 83-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

Bangkok is a poor choice for sun in May: just 10% of days clear historically (n=248). January 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 January — historically the best month for sun in Bangkok.

Every month in Bangkok

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

Historical clear-sky % for Bangkok, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 69% n=248 All destinations →
February 46% n=226 All destinations →
March 35% n=248 All destinations →
April 32% n=240 All destinations →
May ← this page 10% n=248 All destinations →
June 2% n=240 All destinations →
July 0% n=248 All destinations →
August 4% n=248 All destinations →
September 2% n=240 All destinations →
October 11% n=248 All destinations →
November 42% n=240 All destinations →
December 69% n=248 All destinations →

Frequently asked

Does it rain in Bangkok in May?

Yes, frequently. In Bangkok, 70% 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 Bangkok good for sun in May?

Not usually. Bangkok is historically overcast in May: only 10% of days are clear (avg high 92°F, n=248 days, ERA5 2018–2025). January is historically far better for sun here.

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.