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SunnyDays

ERA5 almanac — 8 years of real data

Scottsdale Desert Ridge in September

Historically one of the better months to visit Scottsdale Desert Ridge for sun: 82% of days are clear on average (n=240, avg high 98°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 Scottsdale Desert Ridge 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 Scottsdale Desert Ridge 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 98°F
Late September
16th–end		 82% n=120 98°F
Full month average 82% n=240 98°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 Scottsdale Desert Ridge 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		 100% n=120
Late September
16th–end		 98% n=120
Full month average 99% n=240
11.8 h median sunshine per day 96% of days exceed 8 h sunshine 10% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 82%. Sunshine-based “warm & sunny”: 99%. 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

Scottsdale Desert Ridge is historically one of the best US destinations for sun in September: 82% of days meet the clear bar (avg high 98°F, n=240 days across 8 years). Pack for outdoor activity — this month consistently delivers.

Every month in Scottsdale Desert Ridge

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

Historical clear-sky % for Scottsdale Desert Ridge, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 13% n=248 All destinations →
February 35% n=226 All destinations →
March 46% n=248 All destinations →
April 92% n=240 All destinations →
May 92% n=248 All destinations →
June 94% n=240 All destinations →
July 76% n=248 All destinations →
August 78% n=248 All destinations →
September ← this page 82% n=240 All destinations →
October 85% n=248 All destinations →
November 58% n=240 All destinations →
December 18% 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.