Richmond Hill, Ontario climate data is summarized below. Average annual temperatures range from 3.3 °C (low) to 12.7 °C (high). Annual precipitation averages 900 Millimeters. Richmond Hill is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.41 °C | -1.93 °C | 18 mm |
| February | -10.54 °C | -2.3 °C | 13 mm |
| March | -4.94 °C | 4.58 °C | 59 mm |
| April | 1.85 °C | 12.08 °C | 91 mm |
| May | 8.2 °C | 19.52 °C | 104 mm |
| June | 13.27 °C | 24.13 °C | 118 mm |
| July | 15.87 °C | 26.79 °C | 113 mm |
| August | 15.22 °C | 25.87 °C | 115 mm |
| September | 10.74 °C | 21.3 °C | 83 mm |
| October | 5.46 °C | 13.99 °C | 78 mm |
| November | -0.31 °C | 7.43 °C | 61 mm |
| December | -5.46 °C | 0.84 °C | 47 mm |
| Annual | 3.3 °C | 12.7 °C | 900 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |