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SunnyDays

ERA5 almanac — 8 years of real data

Naples in December

Naples in December is a mixed month for sun: 45% of days historically clear (n=248, avg high 77°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 Naples 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 December

Clear-sky percentage for Naples in December, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early December
1st–15th		 53% n=120 77°F
Late December
16th–end		 38% n=128 77°F
Full month average 45% n=248 77°F

Sunshine & warmth in December

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 Naples in December. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early December
1st–15th		 81% n=120
Late December
16th–end		 66% n=128
Full month average 73% n=248
10.0 h median sunshine per day 83% of days exceed 8 h sunshine 21% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 45%. Sunshine-based “warm & sunny”: 73%. The 28-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

Naples in December is genuinely mixed: 45% of days historically clear (n=248), avg high 77°F — roughly even odds. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Naples

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

Historical clear-sky % for Naples, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 35% n=248 All destinations →
February 41% n=226 All destinations →
March 48% n=248 All destinations →
April 41% n=240 All destinations →
May 28% n=248 All destinations →
June 7% n=240 All destinations →
July 4% n=248 All destinations →
August 2% n=248 All destinations →
September 9% n=240 All destinations →
October 23% n=248 All destinations →
November 44% n=240 All destinations →
December ← this page 45% n=248 All destinations →

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.