Gilliam, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.7 °F (low) to 64.5 °F (high). Annual precipitation averages 41.1 Inches. Gilliam is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 20.3 °F | 37.6 °F | 1.51 in. |
| February | 24.0 °F | 42.8 °F | 1.92 in. |
| March | 33.7 °F | 54.3 °F | 2.8 in. |
| April | 44.0 °F | 65.2 °F | 4.28 in. |
| May | 54.7 °F | 74.6 °F | 5.32 in. |
| June | 64.0 °F | 83.5 °F | 5.13 in. |
| July | 67.8 °F | 87.4 °F | 4.54 in. |
| August | 65.5 °F | 86.2 °F | 3.9 in. |
| September | 56.9 °F | 79.3 °F | 3.88 in. |
| October | 45.7 °F | 67.5 °F | 3.32 in. |
| November | 34.6 °F | 53.7 °F | 2.57 in. |
| December | 25.5 °F | 41.7 °F | 1.91 in. |
| Annual | 44.7 °F | 64.5 °F | 41.08 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |