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SunnyDays

ERA5 almanac — 8 years of real data

Nantucket in July

Nantucket in July: 25% of days see measurable rain, 72°F average high, 24% of days historically clear (n=248, ERA5 2018–2025).

Nantucket in July is historically a poor month for sun: only 24% of days clear across 8 years (n=248, avg high 72°F). August is the clearest month for Nantucket 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 Nantucket 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 Nantucket 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		 10% n=120 72°F
Late July
16th–end		 37% n=128 72°F
Full month average 24% n=248 72°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 Nantucket 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		 18% n=120
Late July
16th–end		 61% n=128
Full month average 40% n=248
13.0 h median sunshine per day 86% of days exceed 8 h sunshine 25% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 24%. Sunshine-based “warm & sunny”: 40%. The 16-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

Nantucket is mostly overcast in July historically: only 24% of days are clear across 8 years (n=248), avg high 72°F. The two halves differ materially (10% early, 37% late) — favour the late half of the month. If you want sun in Nantucket, August is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in August — historically the best month for sun in Nantucket.

Every month in Nantucket

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

Historical clear-sky % for Nantucket, 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 0% n=240 All destinations →
May 0% n=248 All destinations →
June 0% n=240 All destinations →
July ← this page 24% n=248 All destinations →
August 32% n=248 All destinations →
September 6% n=240 All destinations →
October 0% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Nantucket in July?

Sometimes. Nantucket sees measurable rain on 25% of days in July historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Nantucket good for sun in July?

Not usually. Nantucket is historically overcast in July: only 24% of days are clear (avg high 72°F, n=248 days, ERA5 2018–2025). August is historically far better for sun here.

How Nantucket compares in July

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