Romeoville weather in September: Romeoville, Illinois: normal highs, lows, rain and records for September
Romeoville in September has a normal high of 76°F and a normal low of 55°F, a daily mean of 66°F, falling from 81°F on the 1st to 71°F by the 30th. Measurable precipitation falls on 8 days in a normal September, 3.31 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 13°C, 84 mm of precipitation in September.
- NOAA stationRomeoville Weather Office
- Station IDUSC00117457
- Location41.60°N 88.08°W
- Elevation660 ft (201 m)
- From the center2 miles
- Population41,177
- Jan 32° 16°
- Feb 36° 20°
- Mar 49° 30°
- Apr 61° 40°
- May 72° 50°
- Jun 82° 60°
- Jul 85° 65°
- Aug 83° 63°
- Sep 76° 55°
- Oct 64° 44°
- Nov 49° 32°
- Dec 37° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Romeoville in September?
The normal high is 76°F and the normal low 55°F, for a daily mean of 65.9°F. September is 6.9°F cooler than August and 12.2°F warmer than October. September is the 4th warmest month of the year in Romeoville and the 7th 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 63°F and 69°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 |
|---|---|---|---|---|
| September 1 | 81°F | 60°F | 30% | 21% |
| September 8 | 79°F | 58°F | 30% | 20% |
| September 15 | 77°F | 56°F | 29% | 19% |
| September 22 | 74°F | 53°F | 30% | 19% |
| September 30 | 71°F | 50°F | 31% | 19% |
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 | 60°F | 30% | 21% | 13 h 10 min |
| September 2 | 80°F | 60°F | 30% | 21% | 13 h 10 min |
| September 3 | 80°F | 60°F | 30% | 20% | 13 h 10 min |
| September 4 | 80°F | 60°F | 30% | 20% | 13 h |
| September 5 | 80°F | 59°F | 30% | 20% | 13 h |
| September 6 | 79°F | 59°F | 30% | 20% | 13 h |
| September 7 | 79°F | 59°F | 30% | 20% | 12 h 50 min |
| September 8 | 79°F | 58°F | 30% | 20% | 12 h 50 min |
| September 9 | 79°F | 58°F | 30% | 20% | 12 h 50 min |
| September 10 | 78°F | 58°F | 30% | 20% | 12 h 50 min |
| September 11 | 78°F | 57°F | 30% | 20% | 12 h 40 min |
| September 12 | 78°F | 57°F | 29% | 20% | 12 h 40 min |
| September 13 | 78°F | 57°F | 29% | 19% | 12 h 40 min |
| September 14 | 77°F | 56°F | 29% | 19% | 12 h 40 min |
| September 15 | 77°F | 56°F | 29% | 19% | 12 h 30 min |
| September 16 | 77°F | 55°F | 29% | 19% | 12 h 30 min |
| September 17 | 76°F | 55°F | 29% | 19% | 12 h 30 min |
| September 18 | 76°F | 55°F | 29% | 19% | 12 h 20 min |
| September 19 | 76°F | 54°F | 30% | 19% | 12 h 20 min |
| September 20 | 75°F | 54°F | 30% | 19% | 12 h 20 min |
| September 21 | 75°F | 53°F | 30% | 19% | 12 h 20 min |
| September 22 | 74°F | 53°F | 30% | 19% | 12 h 10 min |
| September 23 | 74°F | 53°F | 30% | 19% | 12 h 10 min |
| September 24 | 74°F | 52°F | 30% | 19% | 12 h 10 min |
| September 25 | 73°F | 52°F | 30% | 19% | 12 h 10 min |
| September 26 | 73°F | 51°F | 30% | 19% | 12 h |
| September 27 | 72°F | 51°F | 31% | 19% | 12 h |
| September 28 | 72°F | 51°F | 31% | 19% | 12 h |
| September 29 | 72°F | 50°F | 31% | 19% | 11 h 50 min |
| September 30 | 71°F | 50°F | 31% | 19% | 11 h 50 min |
- Normal high
- 76°FSeptember average
- Normal low
- 55°FSeptember average
- Precipitation
- 3.31 inmonth total
- Days with precipitation
- 80.01 inch or more
- Days at 90°F or more
- 2
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 24
- Days at 80°F or more
- 11
- Sunshine
- 80%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00117457; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Romeoville in September?
On a given September day the chance of 0.01 inch or more is 30% on average, highest around September 30 (31%). In all, 3.31 in falls on 8 days of a normal September, 1 of them with an inch or more.
In a normal September in Romeoville, 2 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00117457.
What are the records for September in Romeoville?
The warmest September temperature on this station's record (since 1992) is 94°F, on September 8, 2002; the coldest is 29°F, on September 23, 1995. The wettest September brought 11.41 in (2019).
The September mean against the 1991-2020 normal of 65.9°F: 2021 69.5°F (+3.5), 2022 65.8°F (−0.1), 2023 66.7°F (+0.8), 2024 69.0°F (+3.1), 2025 67.5°F (+1.6), 2026 69.6°F (+3.7). 5 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 69.5°F | +3.5°F | 1.03 in |
| 2022 | 65.8°F | −0.1°F | 2.59 in |
| 2023 | 66.7°F | +0.8°F | 5.59 in |
| 2024 | 69.0°F | +3.1°F | 2.41 in |
| 2025 | 67.5°F | +1.6°F | 0.71 in |
| 2026 | 69.6°F | +3.7°F | 6.66 in |
Source: records: ACIS, station USC00117457; recent months: ACIS, station USC00117457. Records and recent months use complete months only.
How does September in Romeoville compare across Illinois?
Across the 144 places PlainClimate covers in Illinois, September normal highs run from 72°F in Barrington to 84°F in Anna; Romeoville's is 76°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.