ERA5 almanac — 8 years of real data

Bangkok in January

Bangkok in January: 12% of days see measurable rain, 89°F average high, 69% of days historically clear (n=248, ERA5 2018–2025).

Bangkok in January 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 January

Clear-sky percentage for Bangkok in January, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early January 1st–15th	71%	n=120	89°F
Late January 16th–end	67%	n=128	89°F
Full month average	69%	n=248	89°F

Sunshine & warmth in January

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 January. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early January 1st–15th	96%	n=120
Late January 16th–end	99%	n=128
Full month average	98%	n=248

11.0 h median sunshine per day 96% of days exceed 8 h sunshine 12% 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 January: 69% of days historically (n=248), avg high 89°F. Most trips here in January 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 ← this page	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	69%	n=248	All destinations →

Frequently asked

Does it rain in Bangkok in January?

Rarely. Only 12% of days in Bangkok see measurable rain in January, 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 January?

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

How Bangkok compares in January

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.

→ Bangkok vs Maldives in January — Maldives is 33% clear historically
→ Bangkok vs Phuket in January — Phuket is 25% clear historically

→ Bangkok live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in January — all destinations ranked by January clear-sky %
→ All destinations
→ Raw data (JSON) — buckets, n, source

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.