| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 14.8° | 6.4° | 97.7mm | 10.9 | 62 |
| February | 17.3° | 6.4° | 99.7mm | 7.9 | 76 |
| March | 19.8° | 7.3° | 78.3mm | 8.9 | 82 |
| April | 22.5° | 8.4° | 32.9mm | 4.1 | 92 |
| May | 25.5° | 10.3° | 18.8mm | 2.1 | 96 |
| June | 29.4° | 12.4° | 0.8mm | 0.3 | 90 |
| July | 30.9° | 13.3° | 0mm | 0.1 | 84 |
| August | 30.3° | 13.8° | 0.1mm | 0.1 | 87 |
| September | 30.3° | 13.6° | 1.6mm | 0.6 | 86 |
| October | 26.3° | 11.6° | 19.7mm | 1.8 | 96 |
| November | 19.2° | 8.2° | 50.6mm | 5.9 | 86 |
| December | 14.3° | 5.6° | 81.3mm | 8.9 | 64 |
January in Vallejo averages a daily high of 14.8°C with nights around 6.4°C. Expect roughly 10.9 wet days totalling 97.7mm. Generally workable, with some weather to plan around.
February in Vallejo averages a daily high of 17.3°C with nights around 6.4°C. Expect roughly 7.9 wet days totalling 99.7mm. Comfortable conditions for being outdoors all day.
March in Vallejo averages a daily high of 19.8°C with nights around 7.3°C. Expect roughly 8.9 wet days totalling 78.3mm. Comfortable conditions for being outdoors all day.
April in Vallejo averages a daily high of 22.5°C with nights around 8.4°C. Expect roughly 4.1 wet days totalling 32.9mm. Comfortable conditions for being outdoors all day.
May in Vallejo averages a daily high of 25.5°C with nights around 10.3°C. Rain is rare — about 2.1 wet days and 18.8mm across the month. Comfortable conditions for being outdoors all day.
June in Vallejo averages a daily high of 29.4°C with nights around 12.4°C. Rain is rare — about 0.3 wet days and 0.8mm across the month. Comfortable conditions for being outdoors all day.
July in Vallejo averages a daily high of 30.9°C with nights around 13.3°C. Rain is rare — about 0.1 wet days and 0mm across the month. Comfortable conditions for being outdoors all day.
August in Vallejo averages a daily high of 30.3°C with nights around 13.8°C. Rain is rare — about 0.1 wet days and 0.1mm across the month. Comfortable conditions for being outdoors all day.
September in Vallejo averages a daily high of 30.3°C with nights around 13.6°C. Rain is rare — about 0.6 wet days and 1.6mm across the month. Comfortable conditions for being outdoors all day.
October in Vallejo averages a daily high of 26.3°C with nights around 11.6°C. Rain is rare — about 1.8 wet days and 19.7mm across the month. Comfortable conditions for being outdoors all day.
November in Vallejo averages a daily high of 19.2°C with nights around 8.2°C. Expect roughly 5.9 wet days totalling 50.6mm. Comfortable conditions for being outdoors all day.
December in Vallejo averages a daily high of 14.3°C with nights around 5.6°C. Expect roughly 8.9 wet days totalling 81.3mm. 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. Vallejo peaks at 96.
Based on 30 years of records, April–June scores highest for comfort in Vallejo, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 30.9°C.
February is the wettest, averaging 99.7mm of rain across roughly 7.9 wet days.
December is the coolest month, with average daily highs around 14.3°C.