| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 12.4° | 6° | — | — | 70 |
| February | 14.3° | 6.3° | — | — | 76 |
| March | 16.9° | 6.9° | — | — | 84 |
| April | 19.1° | 7.7° | — | — | 91 |
| May | 21.9° | 9.5° | — | — | 94 |
| June | 25.5° | 11.8° | — | — | 94 |
| July | 28° | 13.4° | — | — | 90 |
| August | 28.4° | 13.8° | — | — | 88 |
| September | 27.8° | 14° | — | — | 91 |
| October | 23.6° | 12.3° | — | — | 94 |
| November | 16.8° | 8.6° | — | — | 84 |
| December | 12.2° | 5.9° | — | — | 69 |
January in Walnut Creek averages a daily high of 12.4°C with nights around 6°C. Generally workable, with some weather to plan around.
February in Walnut Creek averages a daily high of 14.3°C with nights around 6.3°C. Comfortable conditions for being outdoors all day.
March in Walnut Creek averages a daily high of 16.9°C with nights around 6.9°C. Comfortable conditions for being outdoors all day.
April in Walnut Creek averages a daily high of 19.1°C with nights around 7.7°C. Comfortable conditions for being outdoors all day.
May in Walnut Creek averages a daily high of 21.9°C with nights around 9.5°C. Comfortable conditions for being outdoors all day.
June in Walnut Creek averages a daily high of 25.5°C with nights around 11.8°C. Comfortable conditions for being outdoors all day.
July in Walnut Creek averages a daily high of 28°C with nights around 13.4°C. Comfortable conditions for being outdoors all day.
August in Walnut Creek averages a daily high of 28.4°C with nights around 13.8°C. Comfortable conditions for being outdoors all day.
September in Walnut Creek averages a daily high of 27.8°C with nights around 14°C. Comfortable conditions for being outdoors all day.
October in Walnut Creek averages a daily high of 23.6°C with nights around 12.3°C. Comfortable conditions for being outdoors all day.
November in Walnut Creek averages a daily high of 16.8°C with nights around 8.6°C. Comfortable conditions for being outdoors all day.
December in Walnut Creek averages a daily high of 12.2°C with nights around 5.9°C. 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. Walnut Creek peaks at 94.
Based on 30 years of records, April–October scores highest for comfort in Walnut Creek, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 28.4°C.
January is the wettest, averaging —mm of rain across roughly — wet days.
December is the coolest month, with average daily highs around 12.2°C.