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SunnyDays

ERA5 almanac — 8 years of real data

Bangkok in December

Bangkok in December: 11% of days see measurable rain, 89°F average high, 69% of days historically clear (n=248, ERA5 2018–2025).

Bangkok in December is a mixed month for sun: 69% of days historically clear (n=248, avg high 89°F). The outcome varies year to year — check the early/late split below. 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 December

Clear-sky percentage for Bangkok in December, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early December
1st–15th		 62% n=120 89°F
Late December
16th–end		 76% n=128 89°F
Full month average 69% n=248 89°F

Sunshine & warmth in December

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 December. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early December
1st–15th		 97% n=120
Late December
16th–end		 99% n=128
Full month average 98% n=248
10.9 h median sunshine per day 96% of days exceed 8 h sunshine 11% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 69%. Sunshine-based “warm & sunny”: 98%. The 29-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 clears solidly in December: 69% of days historically (n=248), avg high 89°F. Most trips here in December will find more sun than cloud.

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 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 ← this page 69% n=248 All destinations →

Frequently asked

Does it rain in Bangkok in December?

Rarely. Only 11% of days in Bangkok see measurable rain in December, 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 December?

Yes. Bangkok is historically strong for sun in December: 69% of days are clear on average (avg high 89°F, n=248 days, ERA5 2018–2025).

How Bangkok compares in December

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