Click on a day for an hourly weather forecast
The temperatures in Simi Valley in September are comfortable with low of 18°C and and high up to 26°C.
As it is almost never rain during September in Simi Valley the weather is perfect for hanging out outside and exploring all that Simi Valley has to offer.
Our weather forecast can give you a great sense of what weather to expect in Simi Valley in September 2025.
If you’re planning to visit Simi Valley in the near future, we highly recommend that you review the 14 day weather forecast for Simi Valley before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 16° / 8° | 3 | 28 | 0 | 81 mm | Good | Simi Valley in January |
| February | 16° / 8° | 3 | 26 | 0 | 69 mm | Good | Simi Valley in February |
| March | 17° / 9° | 2 | 29 | 0 | 52 mm | Good | Simi Valley in March |
| April | 19° / 11° | 1 | 29 | 0 | 24 mm | Good | Simi Valley in April |
| May | 21° / 14° | 1 | 30 | 0 | 14 mm | Good | Simi Valley in May |
| June | 24° / 17° | 0 | 30 | 0 | 4 mm | Perfect | Simi Valley in June |
| July | 26° / 19° | 0 | 31 | 0 | 12 mm | Perfect | Simi Valley in July |
| August | 26° / 20° | 0 | 31 | 0 | 5 mm | Perfect | Simi Valley in August |
| September | 26° / 18° | 0 | 30 | 0 | 9 mm | Perfect | Simi Valley in September |
| October | 23° / 14° | 1 | 30 | 0 | 16 mm | Perfect | Simi Valley in October |
| November | 19° / 11° | 1 | 29 | 0 | 23 mm | Good | Simi Valley in November |
| December | 15° / 8° | 3 | 28 | 0 | 68 mm | Good | Simi Valley in December |