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SunnyDays

ERA5 almanac — 8 years of real data

Leavenworth in September

Leavenworth in September: 19% of days see measurable rain, 78°F average high, 57% of days historically clear (n=240, ERA5 2018–2025).

Leavenworth in September is a mixed month for sun: 57% of days historically clear (n=240, avg high 78°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 Leavenworth 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 Leavenworth 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		 66% n=120 78°F
Late September
16th–end		 48% n=120 78°F
Full month average 57% n=240 78°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 Leavenworth 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		 91% n=120
Late September
16th–end		 55% n=120
Full month average 73% n=240
11.8 h median sunshine per day 89% of days exceed 8 h sunshine 19% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 57%. Sunshine-based “warm & sunny”: 73%. 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

Leavenworth in September is genuinely mixed: 57% of days historically clear (n=240), avg high 78°F — more clear than cloudy. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Leavenworth

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

Historical clear-sky % for Leavenworth, 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 4% n=240 All destinations →
May 31% n=248 All destinations →
June 55% n=240 All destinations →
July 86% n=248 All destinations →
August 83% n=248 All destinations →
September ← this page 57% n=240 All destinations →
October 16% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Leavenworth in September?

Rarely. Only 19% of days in Leavenworth see measurable rain in September, based on 8 years of ERA5 historical data (n=240 days, 2018–2025). This is a historical average, not a forecast.

Is Leavenworth good for sun in September?

It's mixed. Leavenworth in September is clear on 57% of days historically (avg high 78°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Leavenworth compares in September

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