September
September · August · June
79climate match
United States · 1991–2020
Best time to visit
Sully.
September leads for comfortable weather in Sully: typically 24°C by day, 10.1°C at night, with 92 mm of rain. Based on measured 1991–2020 NOAA station history.
Best comfortSeptember
Typical high24°C
Typical low10.1°C
Rain in September92 mm
July
July · August · June
68climate match
September
September · May · October
73climate match
The weakest month is January, scoring 5 against September’s 79 — days reach only -2.1°C, 26° 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
5-2.1° / -12.3°
Feb
50.5° / -10.3°
Mar
67.7° / -4.2°
Apr
3215.2° / 1.7°
May
5821.1° / 8.3°
Jun
7026.4° / 14.2°
Jul
6928.4° / 16.4°
Aug
7327.3° / 15°
Sep
7924° / 10.1°
Oct
4616.9° / 3.5°
Nov
108.2° / -3.1°
Dec
51° / -8.9°
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | -2.1°C | -12.3°C | 27 mm | 5.5 | 9 h 28 | 5 | Strong coverage |
| February | 0.5°C | -10.3°C | 40 mm | 5.8 | 10 h 32 | 5 | Strong coverage |
| March | 7.7°C | -4.2°C | 56 mm | 6.7 | 11 h 48 | 6 | Strong coverage |
| April | 15.2°C | 1.7°C | 102 mm | 9.5 | 13 h 16 | 32 | Strong coverage |
| May | 21.1°C | 8.3°C | 130 mm | 10.8 | 14 h 30 | 58 | Strong coverage |
| June | 26.4°C | 14.2°C | 139 mm | 10.2 | 15 h 10 | 70 | Strong coverage |
| July | 28.4°C | 16.4°C | 105 mm | 7.7 | 14 h 54 | 69 | Strong coverage |
| August | 27.3°C | 15°C | 113 mm | 8.2 | 13 h 51 | 73 | Strong coverage |
| September | 24°C | 10.1°C | 92 mm | 7.1 | 12 h 25 | 79 | Strong coverage |
| October | 16.9°C | 3.5°C | 79 mm | 7.2 | 11 h 01 | 46 | Strong coverage |
| November | 8.2°C | -3.1°C | 52 mm | 5.8 | 9 h 47 | 10 | Strong coverage |
| December | 1°C | -8.9°C | 42 mm | 6.1 | 9 h 11 | 5 | Strong coverage |
What has changed
Sully 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
+1.0
Feb
+1.0
Mar
+1.3
Apr
+0.2
May
+0.3
Jun
+0.5
Jul
-0.5
Aug
-0.4
Sep
+1.7
Oct
+0.6
Nov
+0.4
Dec
+2.1
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 17.8°C9 Jan 2003 | -36.7°C13 Jan 1974 | 54 mm4 Jan 1971 | 129 mm1960 · driest 0 mm in 1899 | 115 |
| February | 25.0°C27 Feb 2024 | -37.2°C3 Feb 1996 | 64 mm25 Feb 2007 | 93 mm2008 · driest 0 mm in 1896 | 115 |
| March | 32.2°C22 Mar 2026 | -27.2°C1 Mar 1962 | 57 mm31 Mar 1993 | 153 mm1991 · driest 0 mm in 1910 | 114 |
| April | 33.3°C23 Apr 1980 | -17.2°C6 Apr 1982 | 106 mm13 Apr 1991 | 279 mm1991 · driest 0 mm in 1901 | 115 |
| May | 36.7°C22 May 1925 | -7.2°C3 May 2005 | 171 mm26 May 2013 | 410 mm2013 · driest 0 mm in 1914 | 116 |
| June | 38.9°C5 Jun 1911 | 1.7°C1 Jun 1993 | 100 mm10 Jun 1967 | 348 mm2010 · driest 0 mm in 1900 | 106 |
| July | 41.1°C3 Jul 1911 | 4.4°C5 Jul 1972 | 97 mm1 Jul 2014 | 266 mm2025 · driest 0 mm in 1911 | 105 |
| August | 41.7°C5 Aug 1918 | 2.2°C20 Aug 1950 | 176 mm5 Aug 1970 | 336 mm1993 · driest 0 mm in 1929 | 103 |
| September | 38.3°C4 Sep 1925 | -6.1°C29 Sep 1984 | 140 mm30 Sep 1919 | 313 mm2018 · driest 0 mm in 1900 | 111 |
| October | 35.0°C6 Oct 1963 | -16.7°C28 Oct 1925 | 114 mm2 Oct 2019 | 231 mm2019 · driest 0 mm in 1899 | 115 |
| November | 27.8°C1 Nov 1968 | -26.1°C30 Nov 1976 | 85 mm18 Nov 1958 | 155 mm1983 · driest 0 mm in 1901 | 115 |
| December | 20.6°C5 Dec 1998 | -35.6°C19 Dec 1985 | 60 mm14 Dec 2015 | 149 mm2015 · driest 0 mm in 1922 | 114 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 30 | <1 | 5 |
| February | 0 | 0 | 26 | 1 | 5 |
| March | <1 | 0 | 24 | 2 | 3 |
| April | 2 | <1 | 12 | 3 | <1 |
| May | 9 | 1 | 2 | 4 | 0 |
| June | 21 | 6 | 0 | 4 | 0 |
| July | 27 | 11 | 0 | 4 | 0 |
| August | 24 | 7 | 0 | 3 | 0 |
| September | 14 | 4 | <1 | 3 | 0 |
| October | 3 | <1 | 9 | 2 | <1 |
| November | <1 | 0 | 21 | 2 | 1 |
| December | 0 | 0 | 29 | 1 | 5 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | 0% | 14% | 2% | 9% | -6.1–2.0°C |
| February | <1% | 15% | 3% | 13% | -3.6–5.4°C |
| March | 6% | 19% | 5% | 22% | 3.5–11.6°C |
| April | 22% | 27% | 9% | 35% | 12.5–18.4°C |
| May | 47% | 30% | 12% | 40% | 19.5–24.7°C |
| June | 69% | 29% | 12% | 37% | 25.0–29.1°C |
| July | 77% | 23% | 11% | 25% | 27.3–32.0°C |
| August | 76% | 23% | 9% | 28% | 26.3–30.7°C |
| September | 65% | 22% | 9% | 24% | 22.1–26.9°C |
| October | 34% | 18% | 6% | 19% | 14.7–20.8°C |
| November | 5% | 16% | 5% | 13% | 5.3–11.9°C |
| December | 0% | 15% | 3% | 13% | -2.9–4.4°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 4877851
- NOAA station
- USC00133473 · GRINNELL 3 SW
- Station distance
- 17.6 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 28 usable years
- Daylight
- Calculated from latitude 41.58°, 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.