London, Ontario climate data is summarized below. Average annual temperatures range from 4.2 °C (low) to 13.7 °C (high). Annual precipitation averages 504 Millimeters. London is located in USDA Plant Hardiness Zone 6b. 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 | -8.14 °C | -1.08 °C | 8 mm |
| February | -9.54 °C | -1.4 °C | 0 mm |
| March | -3.36 °C | 5.87 °C | 25 mm |
| April | 2.51 °C | 13.53 °C | 33 mm |
| May | 8.63 °C | 20.48 °C | 58 mm |
| June | 13.7 °C | 25.13 °C | 81 mm |
| July | 16.18 °C | 27.3 °C | 91 mm |
| August | 15.54 °C | 26.52 °C | 92 mm |
| September | 11.47 °C | 22.48 °C | 54 mm |
| October | 6.22 °C | 15.36 °C | 33 mm |
| November | 0.65 °C | 8.38 °C | 20 mm |
| December | -3.89 °C | 1.99 °C | 9 mm |
| Annual | 4.2 °C | 13.7 °C | 504 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 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |