Roy, Utah has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.4 °C (low) to 16.7 °C (high). Annual precipitation averages 489.7 Millimeters. Roy 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.2 °C | 2.5 °C | 51.56 mm |
| February | -4.2 °C | 5.4 °C | 43.69 mm |
| March | 0 °C | 11.3 °C | 48.51 mm |
| April | 3.2 °C | 15.2 °C | 59.94 mm |
| May | 7.7 °C | 20.7 °C | 61.47 mm |
| June | 12.1 °C | 26.8 °C | 31.75 mm |
| July | 16.9 °C | 32.3 °C | 12.95 mm |
| August | 16 °C | 31.3 °C | 19.3 mm |
| September | 10.7 °C | 25.3 °C | 34.04 mm |
| October | 4.2 °C | 17.2 °C | 45.72 mm |
| November | -1.3 °C | 9.2 °C | 38.1 mm |
| December | -5.8 °C | 2.7 °C | 42.67 mm |
| Annual | 4.4 °C | 16.7 °C | 489.7 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |