ERA5 almanac — 8 years of real data

Boston in June

Boston in June: 36% of days see measurable rain, 78°F average high, 33% of days historically clear (n=240, ERA5 2018–2025).

Boston in June is historically a poor month for sun: only 33% of days clear across 8 years (n=240, avg high 78°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 June

Clear-sky percentage for Boston in June, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early June 1st–15th	32%	n=120	78°F
Late June 16th–end	34%	n=120	78°F
Full month average	33%	n=240	78°F

Sunshine & warmth in June

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 June. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early June 1st–15th	61%	n=120
Late June 16th–end	75%	n=120
Full month average	68%	n=240

12.8 h median sunshine per day 79% of days exceed 8 h sunshine 36% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 33%. Sunshine-based “warm & sunny”: 68%. The 35-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 June historically: only 33% of days are clear across 8 years (n=240), avg high 78°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 ← this page	33%	n=240	All destinations →
July	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 June?

Sometimes. Boston sees measurable rain on 36% of days in June historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Boston good for sun in June?

It's mixed. Boston in June is clear on 33% of days historically (avg high 78°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Boston compares in June

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 Sun Valley in June — Sun Valley is 33% clear historically
→ Boston vs Aspen in June — Aspen is 34% clear historically
→ Boston vs Austin in June — Austin is 32% clear historically

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