Longmont, Colorado has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 34.9 °F (low) to 65.5 °F (high). Annual precipitation averages 15.3 Inches. Longmont is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.3 °F | 44.1 °F | 0.39 in. |
| February | 17.8 °F | 46.0 °F | 0.52 in. |
| March | 26.0 °F | 56.3 °F | 1.31 in. |
| April | 32.9 °F | 63.0 °F | 1.86 in. |
| May | 42.6 °F | 71.7 °F | 2.78 in. |
| June | 51.5 °F | 84.0 °F | 1.53 in. |
| July | 57.5 °F | 90.1 °F | 1.25 in. |
| August | 55.0 °F | 87.7 °F | 1.82 in. |
| September | 46.4 °F | 79.8 °F | 1.4 in. |
| October | 34.4 °F | 66.1 °F | 1.11 in. |
| November | 24.0 °F | 53.2 °F | 0.79 in. |
| December | 15.4 °F | 43.7 °F | 0.49 in. |
| Annual | 34.9 °F | 65.5 °F | 15.25 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |