St. Mary's, Newfoundland and Labrador climate data is summarized below. Average annual temperatures range from 2.8 °C (low) to 8.5 °C (high). Annual precipitation averages 1226 Millimeters. St. Mary's is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.42 °C | 0.27 °C | 89 mm |
| February | -6.31 °C | -0.84 °C | 89 mm |
| March | -4.78 °C | 0.2 °C | 83 mm |
| April | -1.25 °C | 4.29 °C | 100 mm |
| May | 2.81 °C | 9.08 °C | 92 mm |
| June | 6.86 °C | 13.39 °C | 86 mm |
| July | 11.89 °C | 18.2 °C | 96 mm |
| August | 13.31 °C | 19.46 °C | 88 mm |
| September | 10.25 °C | 16.49 °C | 110 mm |
| October | 6.44 °C | 11.5 °C | 134 mm |
| November | 2.26 °C | 7.19 °C | 138 mm |
| December | -2.04 °C | 2.96 °C | 121 mm |
| Annual | 2.8 °C | 8.5 °C | 1226 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |