Round Rock, Arizona has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.9 °C (low) to 20.9 °C (high). Annual precipitation averages 204 Millimeters. Round Rock is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 7.1 °C | 18.8 mm |
| February | -4.5 °C | 10.7 °C | 14.22 mm |
| March | -1.3 °C | 16.1 °C | 16.76 mm |
| April | 2.4 °C | 20.5 °C | 9.65 mm |
| May | 7.3 °C | 25.9 °C | 12.7 mm |
| June | 12.3 °C | 32.4 °C | 5.33 mm |
| July | 16.5 °C | 34.3 °C | 25.15 mm |
| August | 15.8 °C | 32.7 °C | 31.5 mm |
| September | 10.8 °C | 28.7 °C | 21.59 mm |
| October | 3.6 °C | 21.7 °C | 19.81 mm |
| November | -2.7 °C | 13.6 °C | 13.46 mm |
| December | -6.8 °C | 7.2 °C | 14.99 mm |
| Annual | 3.9 °C | 20.9 °C | 203.96 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |