September
September · June · August
United States · 1991–2020
September leads for comfortable weather in Monon: typically 25.4°C by day, 11.8°C at night, with 81 mm of rain. Based on measured 1991–2020 NOAA station history.
September · June · August
July · August · June
May · October · September
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 bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 0.3°C | -8.7°C | 61 mm | 7.1 | 9 h 32 | 5 | Good coverage |
| February | 2°C | -7.8°C | 49 mm | 6.1 | 10 h 34 | 5 | Good coverage |
| March | 8.6°C | -2.3°C | 64 mm | 7.7 | 11 h 49 | 10 | Good coverage |
| April | 16.3°C | 3.5°C | 94 mm | 9.2 | 13 h 14 | 40 | Good coverage |
| May | 22.2°C | 10.1°C | 100 mm | 9.5 | 14 h 26 | 70 | Good coverage |
| June | 27.1°C | 15.4°C | 114 mm | 8.9 | 15 h 05 | 72 | Good coverage |
| July | 28.5°C | 17°C | 124 mm | 8.5 | 14 h 50 | 64 | Good coverage |
| August | 27.7°C | 15.8°C | 106 mm | 7.8 | 13 h 48 | 72 | Good coverage |
| September | 25.4°C | 11.8°C | 81 mm | 6.9 | 12 h 25 | 80 | Good coverage |
| October | 17.9°C | 5.3°C | 80 mm | 7.8 | 11 h 02 | 52 | Good coverage |
| November | 10°C | -0.4°C | 67 mm | 7.5 | 9 h 50 | 18 | Good coverage |
| December | 2.8°C | -6°C | 55 mm | 7.2 | 9 h 15 | 5 | Good coverage |
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 18.3°C8 Jan 2008 | -30.6°C17 Jan 2009 | 87 mm8 Jan 2008 | 142 mm2024 · driest 9 mm in 2023 | 26 |
| February | 22.2°C12 Feb 1999 | -28.9°C11 Feb 2014 | 78 mm21 Feb 2018 | 166 mm2018 · driest 10 mm in 2004 | 27 |
| March | 28.9°C22 Mar 2012 | -20.6°C1 Mar 2015 | 67 mm8 Mar 2009 | 157 mm2009 · driest 11 mm in 2001 | 28 |
| April | 30.6°C19 Apr 2004 | -8.9°C3 Apr 2021 | 53 mm1 Apr 2026 | 228 mm2026 · driest 11 mm in 2004 | 28 |
| May | 35.0°C28 May 2012 | -3.9°C9 May 2020 | 56 mm31 May 2004 | 138 mm2015 · driest 22 mm in 2026 | 28 |
| June | 36.1°C29 Jun 2012 | 2.2°C1 Jun 2003 | 102 mm8 Jun 2015 | 356 mm2015 · driest 45 mm in 2023 | 27 |
| July | 37.2°C7 Jul 2012 | 5.6°C2 Jul 2001 | 150 mm5 Jul 2003 | 388 mm2003 · driest 45 mm in 2026 | 28 |
| August | 36.1°C30 Aug 2000 | 5.0°C31 Aug 2009 | 145 mm16 Aug 2016 | 331 mm2016 · driest 33 mm in 2003 | 28 |
| September | 36.1°C7 Sep 1998 | 0.0°C24 Sep 2012 | 114 mm28 Sep 2019 | 171 mm2019 · driest 13 mm in 2009 | 27 |
| October | 31.7°C8 Oct 2007 | -5.0°C25 Oct 2006 | 77 mm25 Oct 2021 | 230 mm2001 · driest 6 mm in 2024 | 28 |
| November | 26.7°C1 Nov 2024 | -16.7°C13 Nov 2019 | 40 mm19 Nov 2003 | 113 mm2003 · driest 5 mm in 2023 | 28 |
| December | 20.6°C6 Dec 2001 | -24.4°C27 Dec 2017 | 50 mm15 Dec 2011 | 132 mm2015 · driest 9 mm in 2022 | 27 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 28 | 2 | 5 |
| February | 0 | 0 | 26 | 2 | 5 |
| March | <1 | 0 | 22 | 2 | 2 |
| April | 3 | <1 | 9 | 3 | <1 |
| May | 11 | 3 | <1 | 3 | 0 |
| June | 22 | 8 | 0 | 4 | 0 |
| July | 27 | 11 | 0 | 4 | 0 |
| August | 26 | 8 | 0 | 3 | 0 |
| September | 17 | 5 | 0 | 2 | 0 |
| October | 5 | <1 | 5 | 3 | 0 |
| November | 0 | 0 | 17 | 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% | 22% | 6% | 19% | -2.6–3.3°C |
| February | <1% | 21% | 5% | 21% | -3.7–6.4°C |
| March | 6% | 24% | 8% | 29% | 6.2–12.5°C |
| April | 23% | 31% | 12% | 41% | 14.3–19.0°C |
| May | 49% | 29% | 10% | 33% | 20.0–24.7°C |
| June | 68% | 29% | 13% | 35% | 25.7–28.3°C |
| July | 72% | 27% | 12% | 30% | 26.7–30.7°C |
| August | 75% | 24% | 9% | 23% | 26.5–29.0°C |
| September | 71% | 22% | 8% | 23% | 23.3–27.0°C |
| October | 31% | 24% | 9% | 27% | 16.3–20.6°C |
| November | 5% | 24% | 7% | 23% | 6.8–13.1°C |
| December | <1% | 22% | 6% | 19% | -0.5–7.5°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