Irena, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.3 °F (low) to 61.2 °F (high). Annual precipitation averages 38 Inches. Irena 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.6 °F | 32.4 °F | 0.87 in. |
| February | 18.1 °F | 37.7 °F | 1.34 in. |
| March | 28.4 °F | 50.2 °F | 2.24 in. |
| April | 39.3 °F | 62.2 °F | 3.87 in. |
| May | 51.1 °F | 72.1 °F | 5.48 in. |
| June | 60.9 °F | 81.0 °F | 5.37 in. |
| July | 65.2 °F | 85.7 °F | 4.66 in. |
| August | 62.9 °F | 84.1 °F | 4.11 in. |
| September | 53.9 °F | 76.9 °F | 3.57 in. |
| October | 41.5 °F | 64.8 °F | 3.08 in. |
| November | 29.7 °F | 49.7 °F | 2.02 in. |
| December | 19.4 °F | 37.2 °F | 1.4 in. |
| Annual | 40.3 °F | 61.2 °F | 38.01 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 |