Arnprior, Ontario climate data is summarized below. Average annual temperatures range from 1.7 °C (low) to 12 °C (high). Annual precipitation averages 485 Millimeters. Arnprior is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.49 °C | -4.22 °C | 0 mm |
| February | -13.46 °C | -3.42 °C | 0 mm |
| March | -7.37 °C | 3.09 °C | 17 mm |
| April | 1.07 °C | 12.65 °C | 36 mm |
| May | 7.56 °C | 20.42 °C | 47 mm |
| June | 12.69 °C | 24.36 °C | 76 mm |
| July | 15.08 °C | 26.48 °C | 103 mm |
| August | 14.34 °C | 25.44 °C | 89 mm |
| September | 9.71 °C | 20.84 °C | 53 mm |
| October | 4.54 °C | 13.62 °C | 37 mm |
| November | -1.44 °C | 6.59 °C | 18 mm |
| December | -8.66 °C | -1.38 °C | 9 mm |
| Annual | 1.7 °C | 12 °C | 485 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |