Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Tokyo in August

Tokyo in August: 43% of days see measurable rain, 90°F average high, 29% of days historically clear (n=248, ERA5 2018–2025).

Tokyo in August is historically a poor month for sun: only 29% of days clear across 8 years (n=248, avg high 90°F). May is the clearest month for Tokyo 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 Tokyo 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 August

Clear-sky percentage for Tokyo in August, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early August
1st–15th		 32% n=120 90°F
Late August
16th–end		 27% n=128 90°F
Full month average 29% n=248 90°F

Sunshine & warmth in August

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 Tokyo in August. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early August
1st–15th		 89% n=120
Late August
16th–end		 91% n=128
Full month average 90% n=248
12.2 h median sunshine per day 82% of days exceed 8 h sunshine 43% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 29%. Sunshine-based “warm & sunny”: 90%. The 61-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

Tokyo is mostly overcast in August historically: only 29% of days are clear across 8 years (n=248), avg high 90°F. If you want sun in Tokyo, May is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in May — historically the best month for sun in Tokyo.

Every month in Tokyo

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

Historical clear-sky % for Tokyo, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 3% n=248 All destinations →
April 12% n=240 All destinations →
May 32% n=248 All destinations →
June 27% n=240 All destinations →
July 27% n=248 All destinations →
August ← this page 29% n=248 All destinations →
September 26% n=240 All destinations →
October 21% n=248 All destinations →
November 2% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Tokyo in August?

Sometimes. Tokyo sees measurable rain on 43% of days in August historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Tokyo good for sun in August?

Not usually. Tokyo is historically overcast in August: only 29% of days are clear (avg high 90°F, n=248 days, ERA5 2018–2025). May is historically far better for sun here.

How Tokyo compares in August

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