Fort Irwin, California has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 10.8 °C (low) to 25.6 °C (high). Annual precipitation averages 107.7 Millimeters. 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 | 2.1 °C | 14.9 °C | 19.05 mm |
| February | 3.8 °C | 16.6 °C | 27.94 mm |
| March | 6.3 °C | 20.2 °C | 16.76 mm |
| April | 8.9 °C | 23.7 °C | 3.56 mm |
| May | 13.2 °C | 28.7 °C | 2.03 mm |
| June | 17.8 °C | 34.5 °C | 0.51 mm |
| July | 21.9 °C | 37.6 °C | 4.83 mm |
| August | 21 °C | 37.1 °C | 3.56 mm |
| September | 17.9 °C | 33.2 °C | 4.57 mm |
| October | 10.9 °C | 26.5 °C | 5.08 mm |
| November | 4.1 °C | 19.7 °C | 6.35 mm |
| December | 1.2 °C | 14.1 °C | 13.46 mm |
| Annual | 10.8 °C | 25.6 °C | 107.7 mm |
| 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 : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |