St. Charles weather in September: St. Charles, Missouri: normal highs, lows, rain and records for September
St. Charles in September has a normal high of 81°F and a normal low of 57°F, a daily mean of 69°F, falling from 86°F on the 1st to 76°F by the 30th. Measurable precipitation falls on 10 days in a normal September, 2.97 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 27°C and low of 14°C, 75 mm of precipitation in September.
- NOAA stationSt Charles County Airport
- Station IDUSW00053904
- Location38.93°N 90.43°W
- Elevation436 ft (133 m)
- Population72,458
- Jan 40° 22°
- Feb 45° 26°
- Mar 56° 34°
- Apr 68° 45°
- May 77° 56°
- Jun 86° 65°
- Jul 89° 68°
- Aug 88° 66°
- Sep 81° 57°
- Oct 69° 46°
- Nov 55° 35°
- Dec 44° 27°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is St. Charles in September?
The normal high is 81°F and the normal low 57°F, for a daily mean of 69.1°F. September is 7.8°F cooler than August and 11.6°F warmer than October. September is the 4th warmest month of the year in St. Charles and the 8th wettest. Across the month the normal high falls 10°F, from 86°F on September 1 to 76°F on September 30. From one year to the next September's mean temperature typically moves about 3.0°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 66°F and 72°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 33%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 86°F | 62°F | 31% | 16% |
| September 8 | 84°F | 60°F | 32% | 16% |
| September 15 | 82°F | 57°F | 32% | 15% |
| September 22 | 79°F | 55°F | 32% | 15% |
| September 30 | 76°F | 52°F | 32% | 16% |
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 | 86°F | 62°F | 31% | 16% | 13 h |
| September 2 | 85°F | 62°F | 31% | 16% | 13 h |
| September 3 | 85°F | 62°F | 31% | 16% | 13 h |
| September 4 | 85°F | 61°F | 31% | 16% | 13 h |
| September 5 | 85°F | 61°F | 32% | 15% | 12 h 50 min |
| September 6 | 84°F | 61°F | 32% | 15% | 12 h 50 min |
| September 7 | 84°F | 60°F | 32% | 15% | 12 h 50 min |
| September 8 | 84°F | 60°F | 32% | 16% | 12 h 50 min |
| September 9 | 84°F | 60°F | 32% | 15% | 12 h 50 min |
| September 10 | 83°F | 59°F | 32% | 15% | 12 h 40 min |
| September 11 | 83°F | 59°F | 32% | 15% | 12 h 40 min |
| September 12 | 83°F | 58°F | 32% | 15% | 12 h 40 min |
| September 13 | 82°F | 58°F | 32% | 15% | 12 h 40 min |
| September 14 | 82°F | 58°F | 32% | 15% | 12 h 30 min |
| September 15 | 82°F | 57°F | 32% | 15% | 12 h 30 min |
| September 16 | 81°F | 57°F | 32% | 15% | 12 h 30 min |
| September 17 | 81°F | 57°F | 33% | 15% | 12 h 30 min |
| September 18 | 81°F | 56°F | 33% | 15% | 12 h 20 min |
| September 19 | 80°F | 56°F | 32% | 15% | 12 h 20 min |
| September 20 | 80°F | 55°F | 32% | 15% | 12 h 20 min |
| September 21 | 80°F | 55°F | 32% | 15% | 12 h 20 min |
| September 22 | 79°F | 55°F | 32% | 15% | 12 h 10 min |
| September 23 | 79°F | 54°F | 32% | 15% | 12 h 10 min |
| September 24 | 78°F | 54°F | 32% | 15% | 12 h 10 min |
| September 25 | 78°F | 54°F | 32% | 15% | 12 h 10 min |
| September 26 | 78°F | 53°F | 32% | 15% | 12 h |
| September 27 | 77°F | 53°F | 32% | 16% | 12 h |
| September 28 | 77°F | 53°F | 32% | 16% | 12 h |
| September 29 | 76°F | 52°F | 32% | 16% | 12 h |
| September 30 | 76°F | 52°F | 32% | 16% | 11 h 50 min |
- Normal high
- 81°FSeptember average
- Normal low
- 57°FSeptember average
- Precipitation
- 2.97 inmonth total
- Days with precipitation
- 100.01 inch or more
- Days at 90°F or more
- 5
- Daylight
- 13 h to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 28
- Days at 80°F or more
- 18
- Sunshine
- 81%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00053904; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in St. Charles in September?
On a given September day the chance of 0.01 inch or more is 32% on average, highest around September 17 (33%). In all, 2.97 in falls on 10 days of a normal September, 1 of them with an inch or more.
In a normal September in St. Charles, 5 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00053904.
What are the records for September in St. Charles?
The September mean against the 1991-2020 normal of 69.1°F: 2021 72.5°F (+3.5), 2022 69.2°F (+0.1), 2023 70.5°F (+1.4), 2024 70.8°F (+1.7), 2025 71.4°F (+2.3), 2026 76.3°F (+7.3). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 72.5°F | +3.5°F | 1.34 in |
| 2022 | 69.2°F | +0.1°F | 2.45 in |
| 2023 | 70.5°F | +1.4°F | 1.49 in |
| 2024 | 70.8°F | +1.7°F | 3.75 in |
| 2025 | 71.4°F | +2.3°F | 0.70 in |
| 2026 | 76.3°F | +7.3°F | 1.51 in |
Source: recent months: ACIS, station USW00053904. Records and recent months use complete months only.
How does September in St. Charles compare across Missouri?
Across the 134 places PlainClimate covers in Missouri, September normal highs run from 76°F in Unionville to 85°F in Kennett; St. Charles's is 81°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- St. Charles in August88°F by day, 66°F at night
- St. Charles in October69°F by day, 46°F at night
- St. Charles through the yearEvery month, frost dates, records and recent years
- Missouri in SeptemberThe statewide normal and the warmest and coolest places
- Kennett: Missouri's warmest Septembernormal high 85°F