Foster, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 49.7 °F (low) to 73.8 °F (high). Annual precipitation averages 36.8 Inches. 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 | 27.9 °F | 52.2 °F | 1.56 in. |
| February | 31.7 °F | 56.4 °F | 1.98 in. |
| March | 40.3 °F | 65.3 °F | 2.69 in. |
| April | 48.3 °F | 73.3 °F | 3.55 in. |
| May | 58.4 °F | 80.5 °F | 5.43 in. |
| June | 67.4 °F | 88.8 °F | 4.65 in. |
| July | 71.1 °F | 94.3 °F | 2.75 in. |
| August | 70.0 °F | 94.6 °F | 2.76 in. |
| September | 62.2 °F | 86.6 °F | 3.69 in. |
| October | 50.1 °F | 75.7 °F | 3.39 in. |
| November | 39.2 °F | 63.9 °F | 2.28 in. |
| December | 30.1 °F | 53.7 °F | 2.03 in. |
| Annual | 49.7 °F | 73.8 °F | 36.76 in. |
| 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 : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7b : 5°F to 10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |