Weather in Cornwall for September 2026
Until now, September 2026 in Cornwall is slightly cooler than the historical average by 0.6 °C.
The forecast for the next days in Cornwall predicts temperatures to be around 19 °C, close to the historical average.
In general, the average temperature in Cornwall at the beginning of September is 18.6 °C. As the month progressed, temperatures tended to moderately rise, reaching an average of 19.9 °C by the end of September.
Cornwall experiences heavy rainfall in September, with over 20 rainy days and an average total precipitation 102 mm.
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Cornwall Weather September
Temperatures trend during September in Cornwall
September weather in Cornwall day by day
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| 1 Sept. |  Patchy rain possible | 18° /14° | 2.5 mm | 4 | |
| 2 Sept. | Patchy rain possible | 18° /14° | 3 mm | 3 | |
| 3 Sept. |  Sunny | 18° /14° | 2.8 mm | 4 | |
| 4 Sept. | Sunny | 19° /14° | 3.9 mm | 4 | |
| 5 Sept. |  Partly cloudy | 18° /14° | 3.9 mm | 4 | |
| 6 Sept. | Patchy rain possible | 20° /15° | 7.7 mm | 4 | |
| 7 Sept. |  Patchy light rain with thunder | 19° /14° | 4.5 mm | 4 | |
| 8 Sept. | Patchy rain possible | 17° /14° | 5.9 mm | 4 | |
| 9 Sept. | Partly cloudy | 17° /14° | 5 mm | 4 | |
| 10 Sept. | Light rain shower | 18° /13° | 3.3 mm | 4 | |
| 11 Sept. | Patchy rain possible | 16° /13° | 2.4 mm | 3 | |
| 12 Sept. |  Overcast | 16° /13° | 2.8 mm | 3 | |
| 13 Sept. |  Cloudy | 16° /13° | 1.9 mm | 3 | |
| 14 Sept. | Overcast | 18° /12° | 1.6 mm | 4 | |
| 15 Sept. | Overcast | 17° /13° | 1.7 mm | 3 | |
| 16 Sept. | Patchy rain possible | 18° /13° | 1.5 mm | 4 | |
| 17 Sept. | Light rain shower | 18° /14° | 3.7 mm | 4 | |
| 18 Sept. | Light rain shower | 18° /13° | 0.9 mm | 4 | |
| 19 Sept. | Partly cloudy | 19° /14° | 0.6 mm | 5 | |
| 20 Sept. | Patchy rain possible | 16° /14° | 0.4 mm | 4.1 | |
| 21 Sept. | Sunny | 18° /14° | 0 mm | 4.3 | |
| 22 Sept. | Sunny | 19° /15° | 0 mm | 4 | |
| 23 Sept. | Sunny | 17° /13° | 0 mm | 3.5 | |
| 24 Sept. | Sunny | 18° /13° | 0 mm | 5 | |
| 25 Sept. | Sunny | 19° /15° | 0 mm | 5 | |
| 26 Sept. | Sunny | 22° /14° | 0 mm | 6 | |
| 27 Sept. | Overcast | 18° /15° | 0.5 mm | 5 | |
| 28 Sept. | Sunny | 22° /16° | 0.1 mm | 6 | |
| 29 Sept. | Overcast | 22° /17° | 0.1 mm | 5 | |
| 30 Sept. | Overcast | 18° /16° | 0.3 mm | 4 | |
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Cornwall in September - FAQ
What are the expected maximum and minimum temperatures in Cornwall during September?
How much rainfall should be expected in Cornwall during September?
What are the typical wind conditions in Cornwall during September?
Cornwall water temperatures in September
The average water temperature of the Atlantic Ocean near Cornwall in September is 15.5 °C. At the beginning of September temperatures are around 15.6 °C; by the end of the month they get a bit cooler and reach 15 °C.
- What is the water temperature in Cornwall in September?
- The average water temperature in Cornwall in September is 15.5 °C.
- Can you swim in Cornwall in September?
- Brisk: quick dips and active swimming are fine, but pack a 2–3 mm spring suit if you plan longer sessions or early-morning outings.
September rainfall patterns in Cornwall
UV exposure in Cornwall during September
Quick links
Where is Cornwall?Get accurate weather forecasts for Cornwall, located at latitude 50.416 and longitude -5.073. Stay updated with localized weather information tailored for Cornwall.