Fort Irwin, California has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 51.4 °F (low) to 78 °F (high). Annual precipitation averages 4.2 Inches. Fort Irwin is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.7 °F | 58.9 °F | 0.75 in. |
| February | 38.9 °F | 61.9 °F | 1.1 in. |
| March | 43.4 °F | 68.4 °F | 0.66 in. |
| April | 48.1 °F | 74.6 °F | 0.14 in. |
| May | 55.8 °F | 83.6 °F | 0.08 in. |
| June | 64.1 °F | 94.1 °F | 0.02 in. |
| July | 71.4 °F | 99.6 °F | 0.19 in. |
| August | 69.8 °F | 98.8 °F | 0.14 in. |
| September | 64.3 °F | 91.8 °F | 0.18 in. |
| October | 51.6 °F | 79.7 °F | 0.2 in. |
| November | 39.3 °F | 67.5 °F | 0.25 in. |
| December | 34.2 °F | 57.4 °F | 0.53 in. |
| Annual | 51.4 °F | 78 °F | 4.24 in. |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |