Mason City weather in September: Mason City, Iowa: normal highs, lows, rain and records for September
Mason City in September has a normal high of 74°F and a normal low of 49°F, a daily mean of 61°F, falling from 78°F on the 1st to 68°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 3.45 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 23°C and low of 9°C, 88 mm of precipitation in September.
- NOAA stationMason City Municipal Airport
- Station IDUSW00014940
- Location43.15°N 93.33°W
- Elevation1,225 ft (373 m)
- From the center6 miles
- Population26,948
- Jan 24° 7°
- Feb 29° 11°
- Mar 42° 24°
- Apr 58° 35°
- May 70° 47°
- Jun 80° 57°
- Jul 83° 61°
- Aug 80° 58°
- Sep 74° 49°
- Oct 60° 37°
- Nov 44° 24°
- Dec 30° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Mason City in September?
The normal high is 74°F and the normal low 49°F, for a daily mean of 61.4°F. September is 7.5°F cooler than August and 13.2°F warmer than October. September is the 4th warmest month of the year in Mason City and the 6th wettest. Across the month the normal high falls 10°F, from 78°F on September 1 to 68°F on September 30. From one year to the next September's mean temperature typically moves about 3.1°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 58°F and 65°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 30%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 78°F | 54°F | 29% | 19% |
| September 8 | 77°F | 52°F | 29% | 19% |
| September 15 | 75°F | 49°F | 30% | 19% |
| September 22 | 72°F | 46°F | 30% | 18% |
| September 30 | 68°F | 43°F | 30% | 17% |
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 | 78°F | 54°F | 29% | 19% | 13 h 10 min |
| September 2 | 78°F | 54°F | 29% | 19% | 13 h 10 min |
| September 3 | 78°F | 53°F | 29% | 19% | 13 h 10 min |
| September 4 | 78°F | 53°F | 29% | 19% | 13 h 10 min |
| September 5 | 78°F | 53°F | 29% | 19% | 13 h |
| September 6 | 77°F | 53°F | 29% | 19% | 13 h |
| September 7 | 77°F | 52°F | 29% | 19% | 13 h |
| September 8 | 77°F | 52°F | 29% | 19% | 12 h 50 min |
| September 9 | 77°F | 51°F | 29% | 19% | 12 h 50 min |
| September 10 | 76°F | 51°F | 29% | 19% | 12 h 50 min |
| September 11 | 76°F | 51°F | 29% | 19% | 12 h 50 min |
| September 12 | 76°F | 50°F | 29% | 19% | 12 h 40 min |
| September 13 | 75°F | 50°F | 29% | 19% | 12 h 40 min |
| September 14 | 75°F | 50°F | 29% | 19% | 12 h 40 min |
| September 15 | 75°F | 49°F | 30% | 19% | 12 h 30 min |
| September 16 | 74°F | 49°F | 30% | 18% | 12 h 30 min |
| September 17 | 74°F | 48°F | 30% | 18% | 12 h 30 min |
| September 18 | 74°F | 48°F | 30% | 18% | 12 h 30 min |
| September 19 | 73°F | 48°F | 30% | 18% | 12 h 20 min |
| September 20 | 73°F | 47°F | 30% | 18% | 12 h 20 min |
| September 21 | 72°F | 47°F | 30% | 18% | 12 h 20 min |
| September 22 | 72°F | 46°F | 30% | 18% | 12 h 10 min |
| September 23 | 72°F | 46°F | 30% | 18% | 12 h 10 min |
| September 24 | 71°F | 46°F | 30% | 18% | 12 h 10 min |
| September 25 | 71°F | 45°F | 30% | 18% | 12 h 10 min |
| September 26 | 70°F | 45°F | 30% | 18% | 12 h |
| September 27 | 70°F | 44°F | 30% | 18% | 12 h |
| September 28 | 69°F | 44°F | 30% | 18% | 12 h |
| September 29 | 69°F | 43°F | 30% | 17% | 11 h 50 min |
| September 30 | 68°F | 43°F | 30% | 17% | 11 h 50 min |
- Normal high
- 74°FSeptember average
- Normal low
- 49°FSeptember average
- Precipitation
- 3.45 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 1
- Nights at 32°F or colder
- 1
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 21
- Days at 80°F or more
- 10
- Sunshine
- 78%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014940; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Mason City in September?
On a given September day the chance of 0.01 inch or more is 30% on average, highest around September 20 (30%). In all, 3.45 in falls on 9 days of a normal September, 1 of them with an inch or more.
In a normal September in Mason City, 1 days reach 90°F and 1 nights fall to freezing.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014940.
How humid and windy is Mason City in September?
At 3 p.m. the normal temperature is 67°F with 46% relative humidity and a dew point of 45°F; at 6 a.m. it is 47°F with 87% humidity. The wind averages 10.0 mph, most often from the west-southwest in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 47°F | 44°F | 87% | 8.0 mph | 63% |
| 9 a.m. | 56°F | 47°F | 70% | 11.6 mph | 61% |
| noon | 64°F | 46°F | 52% | 13.2 mph | 56% |
| 3 p.m. | 67°F | 45°F | 46% | 13.8 mph | 60% |
| 6 p.m. | 60°F | 45°F | 57% | 9.1 mph | 67% |
| 9 p.m. | 53°F | 45°F | 74% | 8.3 mph | 70% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014940. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Mason City?
The warmest September temperature on this station's record (since 1948) is 99°F, on September 9, 2013; the coldest is 24°F, on September 29, 1949. The wettest September brought 14.41 in (1965).
The September mean against the 1991-2020 normal of 61.4°F: 2021 63.8°F (+2.4), 2022 61.6°F (+0.2), 2023 66.1°F (+4.7), 2024 65.8°F (+4.4), 2025 65.1°F (+3.7), 2026 65.6°F (+4.2). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 63.8°F | +2.4°F | 1.96 in |
| 2022 | 61.6°F | +0.2°F | 1.26 in |
| 2023 | 66.1°F | +4.7°F | 2.05 in |
| 2024 | 65.8°F | +4.4°F | 0.43 in |
| 2025 | 65.1°F | +3.7°F | 1.12 in |
| 2026 | 65.6°F | +4.2°F | 4.41 in |
Source: records: ACIS, station USW00014940; recent months: ACIS, station USW00014940. Records and recent months use complete months only.
How does September in Mason City compare across Iowa?
Across the 132 places PlainClimate covers in Iowa, September normal highs run from 71°F in Northwood to 79°F in Glenwood; Mason City's is 74°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.