St. Charles weather in August: St. Charles, Missouri: normal highs, lows, rain and records for August
St. Charles in August has a normal high of 88°F and a normal low of 66°F, a daily mean of 77°F, falling from 89°F on the 1st to 86°F by the 31st. Measurable precipitation falls on 9 days in a normal August, 3.68 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 31°C and low of 19°C, 93 mm of precipitation in August.
- 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 August?
The normal high is 88°F and the normal low 66°F, for a daily mean of 76.9°F. August is 1.7°F cooler than July and 7.8°F warmer than September. August is the 2nd warmest month of the year in St. Charles and the 5th wettest. Across the month the normal high falls 3°F, from 89°F on August 1 to 86°F on August 31. From one year to the next August's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Augusts in three average between 74°F and 80°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 31%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| August 1 | 89°F | 68°F | 29% | 17% |
| August 8 | 89°F | 68°F | 30% | 17% |
| August 15 | 88°F | 67°F | 30% | 16% |
| August 22 | 87°F | 65°F | 31% | 16% |
| August 31 | 86°F | 63°F | 31% | 16% |
Every day of August: normal high, low and chance of precipitation (warmest afternoon August 1, coldest night August 31)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| August 1 | 89°F | 68°F | 29% | 17% | 14 h 10 min |
| August 2 | 89°F | 68°F | 30% | 17% | 14 h 10 min |
| August 3 | 89°F | 68°F | 30% | 17% | 14 h 10 min |
| August 4 | 89°F | 68°F | 30% | 17% | 14 h 10 min |
| August 5 | 89°F | 68°F | 30% | 17% | 14 h 10 min |
| August 6 | 89°F | 68°F | 30% | 17% | 14 h |
| August 7 | 89°F | 68°F | 30% | 17% | 14 h |
| August 8 | 89°F | 68°F | 30% | 17% | 14 h |
| August 9 | 89°F | 67°F | 30% | 17% | 14 h |
| August 10 | 89°F | 67°F | 30% | 17% | 13 h 50 min |
| August 11 | 88°F | 67°F | 30% | 17% | 13 h 50 min |
| August 12 | 88°F | 67°F | 30% | 17% | 13 h 50 min |
| August 13 | 88°F | 67°F | 30% | 17% | 13 h 50 min |
| August 14 | 88°F | 67°F | 30% | 17% | 13 h 50 min |
| August 15 | 88°F | 67°F | 30% | 16% | 13 h 40 min |
| August 16 | 88°F | 66°F | 30% | 16% | 13 h 40 min |
| August 17 | 88°F | 66°F | 30% | 16% | 13 h 40 min |
| August 18 | 88°F | 66°F | 30% | 16% | 13 h 40 min |
| August 19 | 88°F | 66°F | 31% | 16% | 13 h 40 min |
| August 20 | 88°F | 66°F | 31% | 16% | 13 h 30 min |
| August 21 | 88°F | 65°F | 31% | 16% | 13 h 30 min |
| August 22 | 87°F | 65°F | 31% | 16% | 13 h 30 min |
| August 23 | 87°F | 65°F | 31% | 16% | 13 h 30 min |
| August 24 | 87°F | 65°F | 31% | 16% | 13 h 20 min |
| August 25 | 87°F | 64°F | 31% | 16% | 13 h 20 min |
| August 26 | 87°F | 64°F | 31% | 16% | 13 h 20 min |
| August 27 | 87°F | 64°F | 31% | 16% | 13 h 20 min |
| August 28 | 86°F | 64°F | 31% | 16% | 13 h 10 min |
| August 29 | 86°F | 63°F | 31% | 16% | 13 h 10 min |
| August 30 | 86°F | 63°F | 31% | 16% | 13 h 10 min |
| August 31 | 86°F | 63°F | 31% | 16% | 13 h 10 min |
- Normal high
- 88°FAugust average
- Normal low
- 66°FAugust average
- Precipitation
- 3.68 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 12
- Daylight
- 14 h 10 min to 13 h 10 minAugust 1 to August 31
- Days at 70°F or more
- 31
- Days at 80°F or more
- 28
- 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 August?
On a given August day the chance of 0.01 inch or more is 30% on average, highest around August 28 (31%). In all, 3.68 in falls on 9 days of a normal August, 1 of them with an inch or more.
In a normal August in St. Charles, 12 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00053904.
What are the records for August in St. Charles?
The August mean against the 1991-2020 normal of 76.9°F: 2021 79.2°F (+2.3), 2022 77.2°F (+0.3), 2023 75.9°F (−1.0), 2024 76.7°F (−0.2), 2025 75.5°F (−1.4), 2026 77.2°F (+0.3). 3 of 6 ran warmer than normal.
| August | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 79.2°F | +2.3°F | 4.27 in |
| 2022 | 77.2°F | +0.3°F | 4.88 in |
| 2023 | 75.9°F | −1.0°F | 4.87 in |
| 2024 | 76.7°F | −0.2°F | 2.56 in |
| 2025 | 75.5°F | −1.4°F | 0.84 in |
| 2026 | 77.2°F | +0.3°F | 2.25 in |
Source: recent months: ACIS, station USW00053904. Records and recent months use complete months only.
How does August in St. Charles compare across Missouri?
Across the 134 places PlainClimate covers in Missouri, August normal highs run from 83°F in Canton to 91°F in Malden; St. Charles's is 88°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.