Waterloo weather in September: Waterloo, Iowa: normal highs, lows, rain and records for September
Waterloo in September has a normal high of 77°F and a normal low of 52°F, a daily mean of 65°F, falling from 81°F on the 1st to 71°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 3.14 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 11°C, 80 mm of precipitation in September.
- NOAA stationWaterloo Municipal Airport
- Station IDUSW00094910
- Location42.55°N 92.40°W
- Elevation868 ft (265 m)
- Population67,477
- Jan 28° 11°
- Feb 33° 15°
- Mar 47° 27°
- Apr 61° 38°
- May 73° 50°
- Jun 82° 61°
- Jul 85° 64°
- Aug 83° 61°
- Sep 77° 52°
- Oct 63° 40°
- Nov 47° 28°
- Dec 34° 17°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Waterloo in September?
The normal high is 77°F and the normal low 52°F, for a daily mean of 64.6°F. September is 7.3°F cooler than August and 13.0°F warmer than October. September is the 4th warmest month of the year in Waterloo and the 6th wettest. Across the month the normal high falls 10°F, from 81°F on September 1 to 71°F on September 30. From one year to the next September's mean temperature typically moves about 2.9°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 62°F and 68°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 29%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 81°F | 58°F | 29% | 18% |
| September 8 | 79°F | 55°F | 29% | 18% |
| September 15 | 77°F | 53°F | 29% | 18% |
| September 22 | 75°F | 50°F | 29% | 18% |
| September 30 | 71°F | 47°F | 29% | 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 | 81°F | 58°F | 29% | 18% | 13 h 10 min |
| September 2 | 81°F | 57°F | 29% | 18% | 13 h 10 min |
| September 3 | 81°F | 57°F | 29% | 18% | 13 h 10 min |
| September 4 | 80°F | 57°F | 29% | 18% | 13 h |
| September 5 | 80°F | 56°F | 29% | 18% | 13 h |
| September 6 | 80°F | 56°F | 29% | 18% | 13 h |
| September 7 | 80°F | 56°F | 29% | 18% | 13 h |
| September 8 | 79°F | 55°F | 29% | 18% | 12 h 50 min |
| September 9 | 79°F | 55°F | 29% | 18% | 12 h 50 min |
| September 10 | 79°F | 55°F | 29% | 18% | 12 h 50 min |
| September 11 | 79°F | 54°F | 29% | 18% | 12 h 40 min |
| September 12 | 78°F | 54°F | 29% | 18% | 12 h 40 min |
| September 13 | 78°F | 54°F | 29% | 18% | 12 h 40 min |
| September 14 | 78°F | 53°F | 29% | 18% | 12 h 40 min |
| September 15 | 77°F | 53°F | 29% | 18% | 12 h 30 min |
| September 16 | 77°F | 52°F | 29% | 18% | 12 h 30 min |
| September 17 | 77°F | 52°F | 29% | 18% | 12 h 30 min |
| September 18 | 76°F | 52°F | 29% | 18% | 12 h 30 min |
| September 19 | 76°F | 51°F | 29% | 18% | 12 h 20 min |
| September 20 | 76°F | 51°F | 29% | 18% | 12 h 20 min |
| September 21 | 75°F | 50°F | 29% | 18% | 12 h 20 min |
| September 22 | 75°F | 50°F | 29% | 18% | 12 h 10 min |
| September 23 | 74°F | 50°F | 29% | 18% | 12 h 10 min |
| September 24 | 74°F | 49°F | 29% | 18% | 12 h 10 min |
| September 25 | 74°F | 49°F | 29% | 18% | 12 h 10 min |
| September 26 | 73°F | 48°F | 29% | 18% | 12 h |
| September 27 | 73°F | 48°F | 29% | 18% | 12 h |
| September 28 | 72°F | 48°F | 29% | 18% | 12 h |
| September 29 | 72°F | 47°F | 29% | 17% | 11 h 50 min |
| September 30 | 71°F | 47°F | 29% | 17% | 11 h 50 min |
- Normal high
- 77°FSeptember average
- Normal low
- 52°FSeptember average
- Precipitation
- 3.14 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 2
- 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
- 22
- Days at 80°F or more
- 11
- Sunshine
- 79%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00094910; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Waterloo in September?
On a given September day the chance of 0.01 inch or more is 29% on average, highest around September 18 (29%). In all, 3.14 in falls on 9 days of a normal September, 1 of them with an inch or more.
In a normal September in Waterloo, 2 days reach 90°F and 1 nights fall to freezing.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00094910.
How humid and windy is Waterloo in September?
At 3 p.m. the normal temperature is 68°F with 46% relative humidity and a dew point of 46°F; at 6 a.m. it is 49°F with 86% humidity. The wind averages 8.8 mph, most often from the 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. | 49°F | 45°F | 86% | 6.5 mph | 62% |
| 9 a.m. | 58°F | 48°F | 70% | 9.9 mph | 67% |
| noon | 66°F | 47°F | 51% | 12.0 mph | 59% |
| 3 p.m. | 68°F | 46°F | 46% | 12.5 mph | 65% |
| 6 p.m. | 62°F | 47°F | 57% | 8.4 mph | 63% |
| 9 p.m. | 55°F | 47°F | 73% | 7.6 mph | 75% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00094910. 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 Waterloo?
The warmest September temperature on Waterloo's official record (since 1895) is 102°F, on September 6, 1922; the coldest is 19°F, on September 30, 1899. The wettest September brought 13.35 in (2018).
The September mean against the 1991-2020 normal of 64.6°F: 2021 67.1°F (+2.5), 2022 65.3°F (+0.7), 2023 69.5°F (+4.9), 2024 68.3°F (+3.7), 2025 67.2°F (+2.6), 2026 67.0°F (+2.4). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 67.1°F | +2.5°F | 1.31 in |
| 2022 | 65.3°F | +0.7°F | 1.13 in |
| 2023 | 69.5°F | +4.9°F | 1.90 in |
| 2024 | 68.3°F | +3.7°F | 0.44 in |
| 2025 | 67.2°F | +2.6°F | 0.89 in |
| 2026 | 67.0°F | +2.4°F | 8.06 in |
Source: records: ACIS, NWS threaded record ALOthr; recent months: ACIS, station USW00094910. Records and recent months use complete months only.
How does September in Waterloo 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; Waterloo's is 77°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.