Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Zion / Springdale in September

Zion / Springdale in September: 12% of days see measurable rain, 79°F average high, 70% of days historically clear (n=240, ERA5 2018–2025).

Historically one of the better months to visit Zion / Springdale for sun: 70% of days are clear on average (n=240, avg high 79°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 Zion / Springdale 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 Zion / Springdale 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		 73% n=120 79°F
Late September
16th–end		 67% n=120 79°F
Full month average 70% n=240 79°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 Zion / Springdale 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		 79% n=120
Full month average 87% n=240
12.0 h median sunshine per day 99% of days exceed 8 h sunshine 12% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 70%. Sunshine-based “warm & sunny”: 87%. The 17-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

Zion / Springdale clears solidly in September: 70% of days historically (n=240), avg high 79°F. Most trips here in September will find more sun than cloud.

Every month in Zion / Springdale

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

Historical clear-sky % for Zion / Springdale, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 1% n=248 All destinations →
April 10% n=240 All destinations →
May 44% n=248 All destinations →
June 84% n=240 All destinations →
July 75% n=248 All destinations →
August 70% n=248 All destinations →
September ← this page 70% n=240 All destinations →
October 20% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Zion / Springdale in September?

Rarely. Only 12% of days in Zion / Springdale 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 Zion / Springdale good for sun in September?

Yes. Zion / Springdale is historically strong for sun in September: 70% of days are clear on average (avg high 79°F, n=240 days, ERA5 2018–2025).

How Zion / Springdale compares in September

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Zion / Springdale 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.