Sarnia, Ontario climate data is summarized below. Average annual temperatures range from 4.4 °C (low) to 13.3 °C (high). Annual precipitation averages 164 Millimeters. Sarnia is located in USDA Plant Hardiness Zone 6b. 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 | -7.9 °C | -1.01 °C | 5 mm |
| February | -8.76 °C | -1.33 °C | 0 mm |
| March | -2.88 °C | 5.76 °C | 8 mm |
| April | 2.24 °C | 12.37 °C | 16 mm |
| May | 8.12 °C | 18.9 °C | 25 mm |
| June | 13.42 °C | 24 °C | 22 mm |
| July | 16.41 °C | 26.41 °C | 26 mm |
| August | 15.98 °C | 25.82 °C | 26 mm |
| September | 11.8 °C | 21.86 °C | 15 mm |
| October | 6.92 °C | 15.5 °C | 10 mm |
| November | 0.97 °C | 8.63 °C | 9 mm |
| December | -3.71 °C | 2.21 °C | 2 mm |
| Annual | 4.4 °C | 13.3 °C | 164 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 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |