September
September · June · May
79climate match
United States · 1991–2020
Best time to visit
Cornwall.
September leads for comfortable weather in Cornwall: typically 24.5°C by day, 13.4°C at night, with 124 mm of rain. Based on measured 1991–2020 NOAA station history.
Best comfortSeptember
Typical high24.5°C
Typical low13.4°C
Rain in September124 mm
July
July · August · June
69climate match
May
May · October · April
74climate match
The weakest month is January, scoring 5 against September’s 79 — days reach only 2.2°C, 22° 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
52.2° / -6.3°
Feb
54.2° / -5.1°
Mar
78.8° / -1.2°
Apr
4016.1° / 4.6°
May
7022.1° / 10.2°
Jun
7326.7° / 15.2°
Jul
5929.6° / 18.1°
Aug
6228.7° / 17.7°
Sep
7924.5° / 13.4°
Oct
4617.5° / 7.3°
Nov
1910.7° / 1.9°
Dec
54.7° / -3°
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 2.2°C | -6.3°C | 104 mm | 8.9 | 9 h 29 | 5 | Strong coverage |
| February | 4.2°C | -5.1°C | 73 mm | 6.8 | 10 h 32 | 5 | Strong coverage |
| March | 8.8°C | -1.2°C | 102 mm | 8 | 11 h 48 | 7 | Strong coverage |
| April | 16.1°C | 4.6°C | 102 mm | 9.4 | 13 h 16 | 40 | Strong coverage |
| May | 22.1°C | 10.2°C | 96 mm | 10.4 | 14 h 29 | 70 | Strong coverage |
| June | 26.7°C | 15.2°C | 118 mm | 9.8 | 15 h 09 | 73 | Strong coverage |
| July | 29.6°C | 18.1°C | 119 mm | 8.5 | 14 h 53 | 59 | Strong coverage |
| August | 28.7°C | 17.7°C | 125 mm | 8.4 | 13 h 50 | 62 | Strong coverage |
| September | 24.5°C | 13.4°C | 124 mm | 7.3 | 12 h 25 | 79 | Strong coverage |
| October | 17.5°C | 7.3°C | 135 mm | 8.3 | 11 h 01 | 46 | Strong coverage |
| November | 10.7°C | 1.9°C | 107 mm | 7.5 | 9 h 48 | 19 | Strong coverage |
| December | 4.7°C | -3°C | 115 mm | 9.2 | 9 h 11 | 5 | Strong coverage |
What has changed
Cornwall runs +0.3°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
+1.2
Feb
+2.0
Mar
-0.2
Apr
-0.5
May
-0.4
Jun
-0.8
Jul
+0.3
Aug
-0.2
Sep
+0.6
Oct
+0.8
Nov
+0.1
Dec
+1.1
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 21.7°C26 Jan 1950 | -26.1°C13 Jan 1912 | 104 mm10 Jan 2024 | 296 mm1996 · driest 1 mm in 1912 | 120 |
| February | 25.0°C22 Feb 2018 | -27.2°C9 Feb 1934 | 80 mm25 Feb 1977 | 218 mm1981 · driest 9 mm in 1987 | 121 |
| March | 30.0°C28 Mar 1945 | -18.9°C6 Mar 1948 | 112 mm30 Mar 1951 | 305 mm1896 · driest 13 mm in 1915 | 121 |
| April | 35.6°C18 Apr 1976 | -13.3°C5 Apr 1982 | 122 mm16 Apr 2007 | 258 mm1983 · driest 23 mm in 1916 | 122 |
| May | 36.1°C27 May 1914 | -3.9°C24 May 1892 | 101 mm29 May 1984 | 284 mm1984 · driest 14 mm in 1911 | 122 |
| June | 38.9°C26 Jun 1952 | 4.4°C16 Jun 2019 | 92 mm1 Jun 1952 | 253 mm2013 · driest 7 mm in 1920 | 124 |
| July | 41.1°C22 Jul 1926 | 4.4°C4 Jul 1892 | 241 mm10 Jul 2023 | 449 mm2023 · driest 27 mm in 1894 | 123 |
| August | 40.6°C7 Aug 1931 | 1.7°C30 Aug 1891 | 151 mm23 Aug 2010 | 448 mm2011 · driest 20 mm in 1918 | 122 |
| September | 40.6°C2 Sep 1953 | -2.2°C29 Sep 1909 | 185 mm17 Sep 1999 | 382 mm2003 · driest 11 mm in 1941 | 126 |
| October | 33.3°C5 Oct 1941 | -6.7°C31 Oct 1897 | 232 mm9 Oct 2005 | 536 mm2005 · driest 0 mm in 1924 | 126 |
| November | 27.8°C1 Nov 2024 | -15.0°C30 Nov 1891 | 105 mm2 Nov 1927 | 229 mm1972 · driest 5 mm in 1905 | 123 |
| December | 22.2°C8 Dec 1998 | -26.7°C30 Dec 1917 | 99 mm20 Dec 1957 | 291 mm1983 · driest 10 mm in 1890 | 124 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 26 | 4 | 4 |
| February | 0 | 0 | 24 | 2 | 2 |
| March | <1 | 0 | 19 | 3 | 2 |
| April | 3 | <1 | 4 | 3 | <1 |
| May | 9 | 3 | 0 | 3 | 0 |
| June | 20 | 7 | 0 | 4 | 0 |
| July | 28 | 15 | 0 | 4 | 0 |
| August | 27 | 13 | 0 | 4 | 0 |
| September | 15 | 3 | 0 | 4 | 0 |
| October | 2 | <1 | <1 | 4 | 0 |
| November | <1 | 0 | 10 | 3 | <1 |
| December | 0 | 0 | 23 | 4 | 2 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | <1% | 28% | 11% | 27% | -1.2–5.1°C |
| February | <1% | 27% | 11% | 25% | 0.1–6.5°C |
| March | 4% | 30% | 12% | 31% | 5.6–12.1°C |
| April | 20% | 33% | 12% | 39% | 13.3–18.3°C |
| May | 52% | 33% | 12% | 37% | 19.9–24.6°C |
| June | 66% | 32% | 12% | 34% | 24.8–29.1°C |
| July | 71% | 29% | 12% | 30% | 28.0–31.3°C |
| August | 72% | 27% | 11% | 25% | 26.9–30.3°C |
| September | 66% | 25% | 11% | 23% | 22.5–26.5°C |
| October | 28% | 23% | 11% | 22% | 15.5–20.2°C |
| November | 4% | 28% | 12% | 29% | 8.2–12.9°C |
| December | <1% | 28% | 11% | 30% | 1.2–7.3°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 5113775
- NOAA station
- USC00309292 · W PT
- Station distance
- 7.6 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 25 usable years
- Daylight
- Calculated from latitude 41.44°, 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.