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The temperatures in Walnut Creek in September are comfortable with low of 16°C and and high up to 29°C.
There shouldn't be any rainy days in in Walnut Creek during September. Having said that, the days are very hot in September so hanging out outside is more recomanded during the after noons and evening time.
Our weather forecast can give you a great sense of what weather to expect in Walnut Creek in September 2025.
If you’re planning to visit Walnut Creek in the near future, we highly recommend that you review the 14 day weather forecast for Walnut Creek before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 15° / 7° | 5 | 26 | 0 | 102 mm | Good | Walnut Creek in January |
| February | 16° / 7° | 4 | 24 | 0 | 98 mm | Good | Walnut Creek in February |
| March | 18° / 8° | 6 | 25 | 0 | 94 mm | Good | Walnut Creek in March |
| April | 21° / 9° | 2 | 28 | 0 | 36 mm | Good | Walnut Creek in April |
| May | 23° / 11° | 1 | 30 | 0 | 18 mm | Perfect | Walnut Creek in May |
| June | 27° / 14° | 0 | 30 | 0 | 6 mm | Perfect | Walnut Creek in June |
| July | 29° / 15° | 0 | 31 | 0 | 2 mm | Good | Walnut Creek in July |
| August | 29° / 15° | 0 | 31 | 0 | 1 mm | Good | Walnut Creek in August |
| September | 29° / 16° | 0 | 30 | 0 | 4 mm | Good | Walnut Creek in September |
| October | 25° / 14° | 2 | 29 | 0 | 31 mm | Perfect | Walnut Creek in October |
| November | 19° / 10° | 3 | 27 | 0 | 55 mm | Good | Walnut Creek in November |
| December | 14° / 7° | 5 | 26 | 0 | 84 mm | Good | Walnut Creek in December |