O'Neill, Nebraska has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36.6 °F (low) to 59.9 °F (high). Annual precipitation averages 25.7 Inches. O'Neill is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.2 °F | 32.9 °F | 0.52 in. |
| February | 15.2 °F | 36.8 °F | 0.62 in. |
| March | 24.4 °F | 47.9 °F | 1.32 in. |
| April | 35.0 °F | 58.7 °F | 2.91 in. |
| May | 46.1 °F | 69.5 °F | 3.98 in. |
| June | 57.1 °F | 80.2 °F | 3.75 in. |
| July | 62.2 °F | 86.7 °F | 3.21 in. |
| August | 59.8 °F | 84.3 °F | 3.2 in. |
| September | 50.3 °F | 76.8 °F | 2.27 in. |
| October | 36.9 °F | 62.3 °F | 2.35 in. |
| November | 24.4 °F | 47.7 °F | 0.9 in. |
| December | 15.1 °F | 35.3 °F | 0.65 in. |
| Annual | 36.6 °F | 59.9 °F | 25.68 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |