Mount Prospect, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41 °F (low) to 58.9 °F (high). Annual precipitation averages 37.7 Inches. Mount Prospect is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.4 °F | 31.3 °F | 2.04 in. |
| February | 19.1 °F | 35.1 °F | 1.93 in. |
| March | 28.3 °F | 45.9 °F | 2.27 in. |
| April | 38.5 °F | 57.9 °F | 3.75 in. |
| May | 49.4 °F | 69.2 °F | 4.58 in. |
| June | 59.3 °F | 79.4 °F | 4.4 in. |
| July | 64.7 °F | 83.7 °F | 3.63 in. |
| August | 63.3 °F | 81.8 °F | 4.02 in. |
| September | 55.3 °F | 75.2 °F | 3.29 in. |
| October | 43.4 °F | 62.5 °F | 3.21 in. |
| November | 32.2 °F | 48.3 °F | 2.46 in. |
| December | 22.3 °F | 36.6 °F | 2.16 in. |
| Annual | 41 °F | 58.9 °F | 37.74 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |