Foster, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.9 °C (low) to 23.2 °C (high). Annual precipitation averages 933.7 Millimeters. Foster is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.3 °C | 11.2 °C | 39.62 mm |
| February | -0.2 °C | 13.6 °C | 50.29 mm |
| March | 4.6 °C | 18.5 °C | 68.33 mm |
| April | 9.1 °C | 22.9 °C | 90.17 mm |
| May | 14.7 °C | 26.9 °C | 137.92 mm |
| June | 19.7 °C | 31.6 °C | 118.11 mm |
| July | 21.7 °C | 34.6 °C | 69.85 mm |
| August | 21.1 °C | 34.8 °C | 70.1 mm |
| September | 16.8 °C | 30.3 °C | 93.73 mm |
| October | 10.1 °C | 24.3 °C | 86.11 mm |
| November | 4 °C | 17.7 °C | 57.91 mm |
| December | -1.1 °C | 12.1 °C | 51.56 mm |
| Annual | 9.9 °C | 23.2 °C | 933.7 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |