St. Catharines, Ontario climate data is summarized below. Average annual temperatures range from 5.9 °C (low) to 13.7 °C (high). Annual precipitation averages 809 Millimeters. St. Catharines 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 | -5.85 °C | 0.31 °C | 33 mm |
| February | -7.03 °C | -0.43 °C | 28 mm |
| March | -1.81 °C | 5.82 °C | 62 mm |
| April | 3.23 °C | 12.29 °C | 83 mm |
| May | 8.82 °C | 19 °C | 78 mm |
| June | 14.8 °C | 23.96 °C | 89 mm |
| July | 17.96 °C | 26.88 °C | 82 mm |
| August | 17.7 °C | 26.25 °C | 69 mm |
| September | 13.66 °C | 22.16 °C | 78 mm |
| October | 8.35 °C | 15.59 °C | 85 mm |
| November | 2.44 °C | 9.17 °C | 63 mm |
| December | -2.09 °C | 3.29 °C | 59 mm |
| Annual | 5.9 °C | 13.7 °C | 809 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 |
| Current Drought Conditions | Normal |