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Weather extremes

How extreme does San Marcos's weather get?

The hottest, coldest, wettest and snowiest days San Marcos has recorded — the outer limits of what its weather can do, and how far they sit beyond a normal day.

Based on 47 years of daily weather observations (1979–present), from the Escondido #2 station 8 km away. Updated through April 2026 — an all-time extreme only changes when a more extreme day actually occurs, so some dates are old. That is normal, not stale data.

The four kinds of extreme

The hottest, coldest, wettest and snowiest single days San Marcos has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day
115°F Sep 6, 2020

That is about 28°F hotter than a normal September afternoon in San Marcos (typical high near 87°F).

The three most extreme on record

1 115°F Sep 6, 2020
2 112°F Jul 22, 2006
3 112°F Jul 6, 2018
❄️ Coldest night
6°F Sep 18, 2021

About 57°F colder than a normal September night in San Marcos (typical low near 63°F).

The three most extreme on record

1 6°F Sep 18, 2021recent
2 25°F Jan 15, 2007
3 26°F Dec 23, 1990
🌧️ Most rain in one day
3.24 in Jan 29, 1980

More rain in a single day than San Marcos usually gets in the whole month of January (typical January total about 3.2 in).

The three most extreme on record

1 3.24 in Jan 29, 1980
2 3.15 in Feb 14, 2019
3 3.14 in Apr 10, 2020

How hot and cold it gets, month by month

The shaded band is the normal range of daily temperatures for each month. The dots show the most extreme it has ever been — so you can see how far beyond a normal day the records really sit.

-10°10°30°50°70°90°110°130° all-time high 115°F JanFebMarAprMayJunJulAugSepOctNovDec
normal range of daily temperatureshottest ever recordedcoldest ever recorded

San Marcos's record heat sits well above even a hot day for the season — September's 115°F is about 28°F beyond a normal hot afternoon. Its record cold is just as far below a normal winter night — the dots mark how rare each extreme really is.

In plain terms

In a normal year, San Marcos's warmest days reach the high 80s°F and its coldest nights drop to the mid-40s°F. But across the record it has gone as high as 115°F and as low as 6°F. A single day has delivered over 3 inches of rain. Those are the outer edges worth knowing if you are moving here, planning a trip, or thinking about a house.
Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Escondido #2 (NOAA GHCN station USC00042863), about 8 km from the city centre.

How we build these numbers →