San Marcos weather in September: San Marcos, Texas: normal highs, lows, rain and records for September
San Marcos in September has a normal high of 91°F and a normal low of 69°F, a daily mean of 80°F, falling from 94°F on the 1st to 87°F by the 30th. Measurable precipitation falls on 7 days in a normal September, 4.03 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 33°C and low of 20°C, 102 mm of precipitation in September.
- NOAA stationSan Marcos
- Station IDUSC00417983
- Location29.88°N 97.95°W
- Elevation665 ft (203 m)
- Population74,316
- Jan 62° 39°
- Feb 67° 42°
- Mar 73° 50°
- Apr 80° 56°
- May 86° 65°
- Jun 92° 72°
- Jul 96° 73°
- Aug 97° 74°
- Sep 91° 69°
- Oct 82° 58°
- Nov 72° 48°
- Dec 64° 41°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is San Marcos in September?
The normal high is 91°F and the normal low 69°F, for a daily mean of 79.5°F. September is 5.7°F cooler than August and 9.4°F warmer than October. September is the 4th warmest month of the year in San Marcos and the 3rd wettest. Across the month the normal high falls 7°F, from 94°F on September 1 to 87°F on September 30. From one year to the next September's mean temperature typically moves about 2.4°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 77°F and 82°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 24%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 94°F | 72°F | 22% | 15% |
| September 8 | 92°F | 71°F | 24% | 16% |
| September 15 | 91°F | 69°F | 23% | 16% |
| September 22 | 89°F | 67°F | 22% | 15% |
| September 30 | 87°F | 64°F | 21% | 14% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 94°F | 72°F | 22% | 15% | 12 h 50 min |
| September 2 | 94°F | 72°F | 22% | 15% | 12 h 50 min |
| September 3 | 94°F | 72°F | 23% | 15% | 12 h 40 min |
| September 4 | 93°F | 72°F | 23% | 15% | 12 h 40 min |
| September 5 | 93°F | 71°F | 23% | 15% | 12 h 40 min |
| September 6 | 93°F | 71°F | 23% | 16% | 12 h 40 min |
| September 7 | 93°F | 71°F | 23% | 16% | 12 h 40 min |
| September 8 | 92°F | 71°F | 24% | 16% | 12 h 40 min |
| September 9 | 92°F | 71°F | 24% | 16% | 12 h 30 min |
| September 10 | 92°F | 70°F | 24% | 16% | 12 h 30 min |
| September 11 | 92°F | 70°F | 24% | 16% | 12 h 30 min |
| September 12 | 91°F | 70°F | 24% | 16% | 12 h 30 min |
| September 13 | 91°F | 70°F | 24% | 16% | 12 h 30 min |
| September 14 | 91°F | 69°F | 23% | 16% | 12 h 20 min |
| September 15 | 91°F | 69°F | 23% | 16% | 12 h 20 min |
| September 16 | 90°F | 69°F | 23% | 16% | 12 h 20 min |
| September 17 | 90°F | 68°F | 23% | 16% | 12 h 20 min |
| September 18 | 90°F | 68°F | 23% | 15% | 12 h 20 min |
| September 19 | 90°F | 68°F | 23% | 15% | 12 h 20 min |
| September 20 | 89°F | 67°F | 23% | 15% | 12 h 10 min |
| September 21 | 89°F | 67°F | 22% | 15% | 12 h 10 min |
| September 22 | 89°F | 67°F | 22% | 15% | 12 h 10 min |
| September 23 | 89°F | 66°F | 22% | 15% | 12 h 10 min |
| September 24 | 88°F | 66°F | 22% | 15% | 12 h 10 min |
| September 25 | 88°F | 66°F | 22% | 14% | 12 h 10 min |
| September 26 | 88°F | 65°F | 21% | 14% | 12 h |
| September 27 | 88°F | 65°F | 21% | 14% | 12 h |
| September 28 | 87°F | 65°F | 21% | 14% | 12 h |
| September 29 | 87°F | 64°F | 21% | 14% | 12 h |
| September 30 | 87°F | 64°F | 21% | 14% | 12 h |
- Normal high
- 91°FSeptember average
- Normal low
- 69°FSeptember average
- Precipitation
- 4.03 inmonth total
- Days with precipitation
- 70.01 inch or more
- Days at 90°F or more
- 19
- Daylight
- 12 h 50 min to 12 hSeptember 1 to September 30
- Days at 70°F or more
- 30
- Days at 80°F or more
- 28
- Sunshine
- 81%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00417983; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in San Marcos in September?
On a given September day the chance of 0.01 inch or more is 23% on average, highest around September 9 (24%). In all, 4.03 in falls on 7 days of a normal September, 1 of them with an inch or more.
In a normal September in San Marcos, 19 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00417983.
What are the records for September in San Marcos?
The warmest September temperature on this station's record (since 1895) is 111°F, on September 5, 2000; the coldest is 39°F, on September 28, 2010. The wettest September brought 12.64 in (1921).
The September mean against the 1991-2020 normal of 79.5°F: 2021 79.5°F (at normal), 2022 80.4°F (+0.9), 2023 85.9°F (+6.4), 2024 81.2°F (+1.7), 2025 82.3°F (+2.8), 2026 87.4°F (+7.9). 5 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 79.5°F | at normal | 4.67 in |
| 2022 | 80.4°F | +0.9°F | 3.16 in |
| 2023 | 85.9°F | +6.4°F | 1.26 in |
| 2024 | 81.2°F | +1.7°F | 1.32 in |
| 2025 | 82.3°F | +2.8°F | 0.63 in |
| 2026 | 87.4°F | +7.9°F | 0.00 in |
Source: records: ACIS, station USC00417983; recent months: ACIS, station USC00417983. Records and recent months use complete months only.
How does September in San Marcos compare across Texas?
Across the 321 places PlainClimate covers in Texas, September normal highs run from 81°F in Hart to 95°F in Presidio; San Marcos's is 91°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.