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SunnyDays

ERA5 almanac — 8 years of real data

Aruba in September

Aruba in September: 27% of days see measurable rain, 90°F average high, 32% of days historically clear (n=240, ERA5 2018–2025).

Aruba in September is historically a poor month for sun: only 32% of days clear across 8 years (n=240, avg high 90°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 Aruba 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 September

Clear-sky percentage for Aruba in September, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early September
1st–15th		 36% n=120 90°F
Late September
16th–end		 27% n=120 90°F
Full month average 32% n=240 90°F

Sunshine & warmth in September

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 Aruba in September. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early September
1st–15th		 99% n=120
Late September
16th–end		 99% n=120
Full month average 99% n=240
11.4 h median sunshine per day 98% of days exceed 8 h sunshine 27% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 32%. Sunshine-based “warm & sunny”: 99%. The 67-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

Aruba is mostly overcast in September historically: only 32% of days are clear across 8 years (n=240), avg high 90°F. Most visitors this month will see more clouds than sun.

Every month in Aruba

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

Historical clear-sky % for Aruba, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 24% n=248 All destinations →
February 22% n=226 All destinations →
March 33% n=248 All destinations →
April 33% n=240 All destinations →
May 39% n=248 All destinations →
June 30% n=240 All destinations →
July 22% n=248 All destinations →
August 24% n=248 All destinations →
September ← this page 32% n=240 All destinations →
October 14% n=248 All destinations →
November 6% n=240 All destinations →
December 12% n=248 All destinations →

Frequently asked

Does it rain in Aruba in September?

Sometimes. Aruba sees measurable rain on 27% of days in September historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Aruba good for sun in September?

It's mixed. Aruba in September is clear on 32% of days historically (avg high 90°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Aruba compares in September

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