Sinclair, Wyoming has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30.8 °F (low) to 56.4 °F (high). Annual precipitation averages 9.5 Inches. Sinclair is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.3 °F | 32.2 °F | 0.5 in. |
| February | 14.6 °F | 34.6 °F | 0.39 in. |
| March | 22.4 °F | 44.8 °F | 0.88 in. |
| April | 28.0 °F | 53.1 °F | 1.0 in. |
| May | 36.8 °F | 63.9 °F | 1.48 in. |
| June | 45.0 °F | 76.3 °F | 0.87 in. |
| July | 51.9 °F | 84.5 °F | 0.73 in. |
| August | 50.0 °F | 82.2 °F | 0.76 in. |
| September | 41.3 °F | 72.7 °F | 0.82 in. |
| October | 30.9 °F | 57.6 °F | 0.89 in. |
| November | 21.8 °F | 42.9 °F | 0.59 in. |
| December | 13.5 °F | 32.2 °F | 0.59 in. |
| Annual | 30.8 °F | 56.4 °F | 9.5 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |