ERA5 almanac — 8 years of real data

Boston in July

Boston in July: 41% of days see measurable rain, 84°F average high, 37% of days historically clear (n=248, ERA5 2018–2025).

Boston in July is historically a poor month for sun: only 37% of days clear across 8 years (n=248, avg high 84°F). 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 Boston 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 July

Clear-sky percentage for Boston in July, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early July 1st–15th	37%	n=120	84°F
Late July 16th–end	37%	n=128	84°F
Full month average	37%	n=248	84°F

Sunshine & warmth in July

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 Boston in July. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early July 1st–15th	88%	n=120
Late July 16th–end	89%	n=128
Full month average	89%	n=248

12.8 h median sunshine per day 83% of days exceed 8 h sunshine 41% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 37%. Sunshine-based “warm & sunny”: 89%. The 52-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

Boston is mostly overcast in July historically: only 37% of days are clear across 8 years (n=248), avg high 84°F. Most visitors this month will see more clouds than sun.

Every month in Boston

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

Historical clear-sky % for Boston, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January	0%	n=248	All destinations →
February	0%	n=226	All destinations →
March	0%	n=248	All destinations →
April	2%	n=240	All destinations →
May	17%	n=248	All destinations →
June	33%	n=240	All destinations →
July ← this page	37%	n=248	All destinations →
August	41%	n=248	All destinations →
September	31%	n=240	All destinations →
October	12%	n=248	All destinations →
November	2%	n=240	All destinations →
December	0%	n=248	All destinations →

Frequently asked

Does it rain in Boston in July?

Sometimes. Boston sees measurable rain on 41% of days in July historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Boston good for sun in July?

It's mixed. Boston in July is clear on 37% of days historically (avg high 84°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Boston compares in July

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Boston this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

→ Boston vs Albany in July — Albany is 37% clear historically
→ Boston vs Charlottesville in July — Charlottesville is 37% clear historically
→ Boston vs Portland in July — Portland is 38% clear historically

→ Boston live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in July — all destinations ranked by July 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.