Brentford, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.1 °C (low) to 12.9 °C (high). Annual precipitation averages 574.8 Millimeters. Brentford is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.5 °C | -5.4 °C | 11.94 mm |
| February | -14.1 °C | -2.3 °C | 15.24 mm |
| March | -7.2 °C | 4.7 °C | 24.38 mm |
| April | -0.3 °C | 13.3 °C | 54.36 mm |
| May | 6.9 °C | 20.4 °C | 81.28 mm |
| June | 13.1 °C | 25.8 °C | 97.79 mm |
| July | 15.6 °C | 28.8 °C | 84.84 mm |
| August | 14.1 °C | 27.9 °C | 59.44 mm |
| September | 8.6 °C | 23.4 °C | 55.12 mm |
| October | 1.1 °C | 15 °C | 55.37 mm |
| November | -6.6 °C | 5.5 °C | 19.3 mm |
| December | -13.1 °C | -2.4 °C | 15.75 mm |
| Annual | 0.1 °C | 12.9 °C | 574.81 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |