San Jose, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.1 °F (low) to 62.9 °F (high). Annual precipitation averages 38.6 Inches. San Jose is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.4 °F | 34.1 °F | 2.11 in. |
| February | 20.8 °F | 39.0 °F | 1.85 in. |
| March | 30.4 °F | 51.1 °F | 2.53 in. |
| April | 41.2 °F | 64.2 °F | 3.89 in. |
| May | 52.7 °F | 74.5 °F | 4.59 in. |
| June | 62.1 °F | 83.2 °F | 4.51 in. |
| July | 65.1 °F | 86.1 °F | 4.18 in. |
| August | 62.8 °F | 84.6 °F | 3.51 in. |
| September | 54.6 °F | 79.6 °F | 3.32 in. |
| October | 43.0 °F | 66.9 °F | 3.09 in. |
| November | 32.1 °F | 51.7 °F | 2.8 in. |
| December | 23.1 °F | 39.4 °F | 2.2 in. |
| Annual | 42.1 °F | 62.9 °F | 38.58 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |