Ulm, Arkansas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.5 °C (low) to 22.4 °C (high). Annual precipitation averages 1287.3 Millimeters. Ulm is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.4 °C | 9.7 °C | 97.79 mm |
| February | 2.1 °C | 12.6 °C | 109.22 mm |
| March | 6.3 °C | 17.3 °C | 132.08 mm |
| April | 11.2 °C | 22.8 °C | 147.32 mm |
| May | 16.7 °C | 27.3 °C | 124.71 mm |
| June | 21.1 °C | 31.4 °C | 84.84 mm |
| July | 22.6 °C | 32.9 °C | 85.34 mm |
| August | 21.6 °C | 32.7 °C | 74.93 mm |
| September | 17.6 °C | 29.7 °C | 74.93 mm |
| October | 11.1 °C | 23.9 °C | 108.97 mm |
| November | 5.6 °C | 16.7 °C | 107.7 mm |
| December | 2 °C | 11.4 °C | 139.45 mm |
| Annual | 11.5 °C | 22.4 °C | 1287.28 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |