Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Mazatlán in September

Mazatlán in September: 60% of days see measurable rain, 87°F average high, 15% of days historically clear (n=240, ERA5 2018–2025).

Mazatlán in September is historically a poor month for sun: only 15% of days clear across 8 years (n=240, avg high 87°F). March is the clearest month for Mazatlán historically. 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 Mazatlán 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 Mazatlán 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		 12% n=120 87°F
Late September
16th–end		 18% n=120 87°F
Full month average 15% n=240 87°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 Mazatlán 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		 86% n=120
Late September
16th–end		 92% n=120
Full month average 89% n=240
11.0 h median sunshine per day 83% of days exceed 8 h sunshine 60% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 15%. Sunshine-based “warm & sunny”: 89%. The 74-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

Mazatlán is a poor choice for sun in September: just 15% of days clear historically (n=240). March is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in March — historically the best month for sun in Mazatlán.

Every month in Mazatlán

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

Historical clear-sky % for Mazatlán, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 91% n=248 All destinations →
February 85% n=226 All destinations →
March 98% n=248 All destinations →
April 98% n=240 All destinations →
May 97% n=248 All destinations →
June 62% n=240 All destinations →
July 33% n=248 All destinations →
August 16% n=248 All destinations →
September ← this page 15% n=240 All destinations →
October 58% n=248 All destinations →
November 90% n=240 All destinations →
December 93% n=248 All destinations →

Frequently asked

Does it rain in Mazatlán in September?

Yes, frequently. In Mazatlán, 60% of days in September see measurable rain, based on 8 years of ERA5 historical data (n=240 days, 2018–2025). This is a historical average, not a forecast.

Is Mazatlán good for sun in September?

Not usually. Mazatlán is historically overcast in September: only 15% of days are clear (avg high 87°F, n=240 days, ERA5 2018–2025). March is historically far better for sun here.

How Mazatlán compares in September

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