Brewster, Kansas has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 2.8 °C (low) to 18.9 °C (high). Annual precipitation averages 495.1 Millimeters. Brewster is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.9 °C | 5.8 °C | 8.13 mm |
| February | -7.8 °C | 7.4 °C | 12.45 mm |
| March | -3.6 °C | 13.2 °C | 21.84 mm |
| April | 1.1 °C | 17.9 °C | 42.42 mm |
| May | 7.3 °C | 23.3 °C | 69.09 mm |
| June | 13.3 °C | 29.9 °C | 72.9 mm |
| July | 16.4 °C | 32.9 °C | 85.09 mm |
| August | 15.3 °C | 31.4 °C | 77.47 mm |
| September | 10.1 °C | 27.1 °C | 39.12 mm |
| October | 2.6 °C | 19.6 °C | 39.37 mm |
| November | -3.8 °C | 11.9 °C | 16.76 mm |
| December | -8.3 °C | 6.3 °C | 10.41 mm |
| Annual | 2.8 °C | 18.9 °C | 495.05 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |