| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 14.4° | 3.4° | 106mm | 10.4 | 61 |
| February | 16.9° | 4.6° | 106.3mm | 8.6 | 73 |
| March | 19.5° | 6.5° | 83.9mm | 9.2 | 80 |
| April | 22.6° | 8° | 30.1mm | 4.5 | 91 |
| May | 27° | 11° | 16.8mm | 2.9 | 94 |
| June | 31.9° | 14.1° | 3mm | 0.8 | 79 |
| July | 35° | 15.5° | 0.1mm | 0.1 | 68 |
| August | 34.3° | 15° | 0.4mm | 0.2 | 70 |
| September | 32.1° | 13.5° | 2.6mm | 0.9 | 78 |
| October | 26.4° | 9.9° | 22.7mm | 3 | 94 |
| November | 19° | 5.6° | 56mm | 7.5 | 82 |
| December | 14.3° | 3.3° | 125.7mm | 10.4 | 61 |
January in Vacaville averages a daily high of 14.4°C with nights around 3.4°C. Expect roughly 10.4 wet days totalling 106mm. Generally workable, with some weather to plan around.
February in Vacaville averages a daily high of 16.9°C with nights around 4.6°C. Expect roughly 8.6 wet days totalling 106.3mm. Generally workable, with some weather to plan around.
March in Vacaville averages a daily high of 19.5°C with nights around 6.5°C. Expect roughly 9.2 wet days totalling 83.9mm. Comfortable conditions for being outdoors all day.
April in Vacaville averages a daily high of 22.6°C with nights around 8°C. Expect roughly 4.5 wet days totalling 30.1mm. Comfortable conditions for being outdoors all day.
May in Vacaville averages a daily high of 27°C with nights around 11°C. Rain is rare — about 2.9 wet days and 16.8mm across the month. Comfortable conditions for being outdoors all day.
June in Vacaville averages a daily high of 31.9°C with nights around 14.1°C. Rain is rare — about 0.8 wet days and 3mm across the month. Comfortable conditions for being outdoors all day.
July in Vacaville averages a daily high of 35°C with nights around 15.5°C. Rain is rare — about 0.1 wet days and 0.1mm across the month. Generally workable, with some weather to plan around.
August in Vacaville averages a daily high of 34.3°C with nights around 15°C. Rain is rare — about 0.2 wet days and 0.4mm across the month. Generally workable, with some weather to plan around.
September in Vacaville averages a daily high of 32.1°C with nights around 13.5°C. Rain is rare — about 0.9 wet days and 2.6mm across the month. Comfortable conditions for being outdoors all day.
October in Vacaville averages a daily high of 26.4°C with nights around 9.9°C. Expect roughly 3 wet days totalling 22.7mm. Comfortable conditions for being outdoors all day.
November in Vacaville averages a daily high of 19°C with nights around 5.6°C. Expect roughly 7.5 wet days totalling 56mm. Comfortable conditions for being outdoors all day.
December in Vacaville averages a daily high of 14.3°C with nights around 3.3°C. Expect roughly 10.4 wet days totalling 125.7mm. Generally workable, with some weather to plan around.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Vacaville peaks at 94.
Based on 30 years of records, April–May scores highest for comfort in Vacaville, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 35°C.
December is the wettest, averaging 125.7mm of rain across roughly 10.4 wet days.
December is the coolest month, with average daily highs around 14.3°C.