Dexter, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.8 °C (low) to 17.3 °C (high). Annual precipitation averages 1152.4 Millimeters. Dexter is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.5 °C | 8.8 °C | 150.37 mm |
| February | 1.7 °C | 10.9 °C | 120.65 mm |
| March | 2.7 °C | 13.4 °C | 130.81 mm |
| April | 4.3 °C | 15.6 °C | 112.27 mm |
| May | 6.9 °C | 19.3 °C | 82.3 mm |
| June | 9.2 °C | 22.4 °C | 46.74 mm |
| July | 11.3 °C | 27.1 °C | 11.43 mm |
| August | 11.1 °C | 27.6 °C | 11.94 mm |
| September | 9.1 °C | 24.6 °C | 39.88 mm |
| October | 6.2 °C | 18.1 °C | 92.2 mm |
| November | 3.6 °C | 11.7 °C | 171.45 mm |
| December | 1.4 °C | 8.1 °C | 182.37 mm |
| Annual | 5.8 °C | 17.3 °C | 1152.41 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |