September
September · August · June
80climate match
United States · 1991–2020
Best time to visit
Grant Park.
September leads for comfortable weather in Grant Park: typically 24.9°C by day, 11.4°C at night, with 84 mm of rain. Based on measured 1991–2020 NOAA station history.
Best comfortSeptember
Typical high24.9°C
Typical low11.4°C
Rain in September84 mm
July
July · August · June
68climate match
May
May · September · October
72climate match
The weakest month is January, scoring 5 against September’s 80 — days reach only -0.3°C, 24° below the 24°C the score treats as ideal.
Month by month
The whole year,
without the guesswork.
The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.
Jan
5-0.3° / -9.3°
Feb
52.2° / -7.7°
Mar
108.6° / -2.5°
Apr
3715.8° / 3.1°
May
6621.9° / 9.4°
Jun
7127.1° / 15°
Jul
6628.6° / 16.9°
Aug
7227.7° / 15.8°
Sep
8024.9° / 11.4°
Oct
4817.7° / 5°
Nov
159.5° / -0.8°
Dec
52.7° / -6.1°
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | -0.3°C | -9.3°C | 59 mm | 8.1 | 9 h 30 | 5 | Strong coverage |
| February | 2.2°C | -7.7°C | 49 mm | 7.2 | 10 h 33 | 5 | Strong coverage |
| March | 8.6°C | -2.5°C | 59 mm | 8.4 | 11 h 48 | 10 | Strong coverage |
| April | 15.8°C | 3.1°C | 93 mm | 10.4 | 13 h 15 | 37 | Strong coverage |
| May | 21.9°C | 9.4°C | 108 mm | 10.4 | 14 h 28 | 66 | Strong coverage |
| June | 27.1°C | 15°C | 130 mm | 9.5 | 15 h 08 | 71 | Strong coverage |
| July | 28.6°C | 16.9°C | 110 mm | 8.6 | 14 h 52 | 66 | Strong coverage |
| August | 27.7°C | 15.8°C | 109 mm | 7.7 | 13 h 49 | 72 | Strong coverage |
| September | 24.9°C | 11.4°C | 84 mm | 7.1 | 12 h 25 | 80 | Strong coverage |
| October | 17.7°C | 5°C | 91 mm | 8.7 | 11 h 02 | 48 | Strong coverage |
| November | 9.5°C | -0.8°C | 67 mm | 8.1 | 9 h 49 | 15 | Strong coverage |
| December | 2.7°C | -6.1°C | 57 mm | 7.6 | 9 h 13 | 5 | Strong coverage |
What has changed
Grant Park runs +0.7°C
on the 1961–1990 baseline.
Each bar compares the 2011–2025 daytime average for that month against the same month in 1961–1990, measured at the same station. Months where the older record is too thin to compare are left blank.
Jan
+1.4
Feb
+1.2
Mar
+1.5
Apr
0.0
May
+0.2
Jun
0.0
Jul
-0.6
Aug
+0.1
Sep
+1.1
Oct
+0.6
Nov
+0.2
Dec
+2.6
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 18.9°C8 Jan 2008 | -33.3°C16 Jan 1977 | 76 mm11 Jan 2020 | 130 mm2005 · driest 3 mm in 1986 | 62 |
| February | 22.8°C26 Feb 2000 | -30.6°C11 Feb 2014 | 64 mm1 Feb 1968 | 169 mm2018 · driest 12 mm in 1977 | 62 |
| March | 29.4°C22 Mar 2012 | -22.8°C4 Mar 2002 | 56 mm8 Mar 2009 | 144 mm1977 · driest 18 mm in 2001 | 63 |
| April | 32.8°C25 Apr 1986 | -13.9°C7 Apr 1982 | 99 mm14 Apr 1981 | 295 mm1981 · driest 18 mm in 1971 | 63 |
| May | 35.6°C28 May 2018 | -4.4°C9 May 2020 | 74 mm29 May 1989 | 225 mm2019 · driest 10 mm in 1964 | 62 |
| June | 40.0°C25 Jun 1988 | 0.6°C11 Jun 1972 | 149 mm13 Jun 1972 | 288 mm2015 · driest 13 mm in 1991 | 63 |
| July | 38.3°C6 Jul 1988 | 5.0°C6 Jul 1972 | 93 mm21 Jul 2003 | 335 mm2003 · driest 16 mm in 1991 | 62 |
| August | 40.0°C1 Aug 1988 | 3.3°C29 Aug 1986 | 134 mm17 Aug 1968 | 340 mm2007 · driest 23 mm in 1996 | 62 |
| September | 36.7°C10 Sep 1983 | -2.2°C23 Sep 1995 | 81 mm9 Sep 1992 | 296 mm2008 · driest 0 mm in 1979 | 63 |
| October | 33.3°C6 Oct 1963 | -7.8°C28 Oct 1976 | 92 mm24 Oct 2021 | 225 mm2021 · driest 7 mm in 1964 | 63 |
| November | 26.1°C2 Nov 2016 | -16.7°C22 Nov 2015 | 131 mm27 Nov 1990 | 243 mm1985 · driest 12 mm in 2021 | 63 |
| December | 21.1°C4 Dec 2012 | -33.9°C22 Dec 1989 | 89 mm24 Dec 1965 | 160 mm1971 · driest 12 mm in 1995 | 63 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 28 | 2 | 6 |
| February | 0 | 0 | 25 | 1 | 5 |
| March | <1 | 0 | 22 | 2 | 2 |
| April | 3 | <1 | 9 | 3 | <1 |
| May | 11 | 3 | <1 | 4 | 0 |
| June | 22 | 9 | 0 | 3 | 0 |
| July | 27 | 12 | 0 | 4 | 0 |
| August | 26 | 9 | 0 | 3 | 0 |
| September | 16 | 5 | <1 | 2 | 0 |
| October | 5 | <1 | 6 | 3 | <1 |
| November | <1 | 0 | 18 | 2 | <1 |
| December | 0 | 0 | 26 | 2 | 4 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | 0% | 24% | 5% | 25% | -4.7–3.2°C |
| February | <1% | 24% | 4% | 25% | -2.3–5.8°C |
| March | 5% | 28% | 7% | 36% | 4.9–12.1°C |
| April | 18% | 35% | 12% | 46% | 13.5–18.6°C |
| May | 44% | 32% | 11% | 39% | 19.0–25.2°C |
| June | 65% | 30% | 11% | 34% | 25.2–28.8°C |
| July | 72% | 28% | 11% | 31% | 27.3–30.8°C |
| August | 75% | 24% | 10% | 25% | 26.3–29.3°C |
| September | 65% | 24% | 9% | 27% | 23.1–26.7°C |
| October | 29% | 27% | 9% | 31% | 15.6–20.1°C |
| November | 5% | 27% | 8% | 32% | 6.1–12.3°C |
| December | 0% | 27% | 7% | 30% | -1.7–5.8°C |
A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.
The evidence behind this page
Nearby, measured,
and named.
- Place identity
- GeoNames 4894387
- NOAA station
- USC00125174 · LOWELL WWTP
- Station distance
- 19.3 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 29 usable years
- Daylight
- Calculated from latitude 41.24°, mid-month, sunrise to sunset including refraction. Not a station measurement.
- Important limit
- Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.