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SunnyDays

ERA5 almanac — 8 years of real data

Newport Beach in September

Historically one of the better months to visit Newport Beach for sun: 70% of days are clear on average (n=240, avg high 76°F). Every percentage here is a historical average from 8 years of ERA5 data — 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 Newport Beach 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 Newport Beach 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		 82% n=120 76°F
Late September
16th–end		 59% n=120 76°F
Full month average 70% n=240 76°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 Newport Beach 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		 93% n=120
Late September
16th–end		 68% n=120
Full month average 80% n=240
11.5 h median sunshine per day 94% of days exceed 8 h sunshine 7% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 70%. Sunshine-based “warm & sunny”: 80%.

Bottom line

Newport Beach clears solidly in September: 70% of days historically (n=240), avg high 76°F. The two halves differ materially (82% early, 59% late) — favour the early half of the month. Most trips here in September will find more sun than cloud.

Every month in Newport Beach

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

Historical clear-sky % for Newport Beach, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 8% n=248 All destinations →
February 6% n=226 All destinations →
March 2% n=248 All destinations →
April 10% n=240 All destinations →
May 8% n=248 All destinations →
June 25% n=240 All destinations →
July 71% n=248 All destinations →
August 88% n=248 All destinations →
September ← this page 70% n=240 All destinations →
October 49% n=248 All destinations →
November 22% n=240 All destinations →
December 5% 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.