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SunnyDays

ERA5 almanac — 8 years of real data

Florence in September

Florence in September: 32% of days see measurable rain, 80°F average high, 50% of days historically clear (n=240, ERA5 2018–2025).

Florence in September is a mixed month for sun: 50% of days historically clear (n=240, avg high 80°F). The outcome varies year to year — check the early/late split below. 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 Florence 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 Florence 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		 62% n=120 80°F
Late September
16th–end		 38% n=120 80°F
Full month average 50% n=240 80°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 Florence 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		 95% n=120
Late September
16th–end		 71% n=120
Full month average 83% n=240
11.7 h median sunshine per day 87% of days exceed 8 h sunshine 32% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 50%. Sunshine-based “warm & sunny”: 83%. The 33-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

Florence in September is genuinely mixed: 50% of days historically clear (n=240), avg high 80°F — roughly even odds. The two halves differ materially (62% early, 38% late) — favour the early half of the month. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Florence

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

Historical clear-sky % for Florence, 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 16% n=240 All destinations →
May 27% n=248 All destinations →
June 56% n=240 All destinations →
July 65% n=248 All destinations →
August 57% n=248 All destinations →
September ← this page 50% n=240 All destinations →
October 29% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Florence in September?

Sometimes. Florence sees measurable rain on 32% of days in September historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Florence good for sun in September?

It's mixed. Florence in September is clear on 50% of days historically (avg high 80°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Florence compares in September

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