Grimes, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 48.7 °F (low) to 75 °F (high). Annual precipitation averages 18.5 Inches. Grimes is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.8 °F | 55.5 °F | 3.51 in. |
| February | 41.2 °F | 60.9 °F | 3.9 in. |
| March | 43.7 °F | 66.4 °F | 2.22 in. |
| April | 46.2 °F | 72.5 °F | 1.32 in. |
| May | 52.7 °F | 80.7 °F | 0.77 in. |
| June | 58.0 °F | 88.6 °F | 0.26 in. |
| July | 60.2 °F | 93.9 °F | 0.01 in. |
| August | 58.7 °F | 93.0 °F | 0.13 in. |
| September | 55.5 °F | 89.3 °F | 0.18 in. |
| October | 49.1 °F | 79.2 °F | 0.88 in. |
| November | 42.1 °F | 64.8 °F | 1.93 in. |
| December | 38.2 °F | 55.6 °F | 3.36 in. |
| Annual | 48.7 °F | 75 °F | 18.47 in. |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |