Duncan, Arizona has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 7.2 °C (low) to 26.8 °C (high). Annual precipitation averages 267.5 Millimeters. Duncan is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.7 °C | 15.8 °C | 21.59 mm |
| February | -0.7 °C | 18.4 °C | 20.57 mm |
| March | 1.9 °C | 22.2 °C | 13.97 mm |
| April | 4.9 °C | 26.9 °C | 4.57 mm |
| May | 9.6 °C | 31.8 °C | 7.37 mm |
| June | 15.1 °C | 36.9 °C | 6.35 mm |
| July | 19.3 °C | 36.8 °C | 43.18 mm |
| August | 18.8 °C | 35.4 °C | 54.1 mm |
| September | 14.7 °C | 33.1 °C | 32.26 mm |
| October | 7.4 °C | 28.2 °C | 18.54 mm |
| November | 1.1 °C | 20.9 °C | 17.27 mm |
| December | -2.6 °C | 15.4 °C | 27.69 mm |
| Annual | 7.2 °C | 26.8 °C | 267.46 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |