Barstow, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.1 °F (low) to 60.2 °F (high). Annual precipitation averages 38.1 Inches. Barstow is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.5 °F | 30.6 °F | 1.54 in. |
| February | 18.1 °F | 35.1 °F | 1.75 in. |
| March | 28.8 °F | 47.8 °F | 2.52 in. |
| April | 39.9 °F | 61.0 °F | 3.69 in. |
| May | 51.7 °F | 72.3 °F | 4.82 in. |
| June | 61.8 °F | 81.8 °F | 4.84 in. |
| July | 65.4 °F | 85.0 °F | 4.3 in. |
| August | 63.3 °F | 83.1 °F | 3.97 in. |
| September | 55.0 °F | 76.9 °F | 3.49 in. |
| October | 43.2 °F | 64.0 °F | 2.84 in. |
| November | 31.2 °F | 48.8 °F | 2.27 in. |
| December | 20.7 °F | 36.0 °F | 2.02 in. |
| Annual | 41.1 °F | 60.2 °F | 38.05 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |