Rio Grande City, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 63.4 °F (low) to 86.8 °F (high). Annual precipitation averages 20.2 Inches. Rio Grande City is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 47.6 °F | 70.9 °F | 0.7 in. |
| February | 51.6 °F | 75.8 °F | 0.77 in. |
| March | 57.8 °F | 82.1 °F | 0.95 in. |
| April | 64.3 °F | 88.6 °F | 1.38 in. |
| May | 71.0 °F | 93.7 °F | 2.7 in. |
| June | 74.8 °F | 98.1 °F | 2.36 in. |
| July | 75.9 °F | 99.3 °F | 1.56 in. |
| August | 75.8 °F | 99.8 °F | 1.25 in. |
| September | 72.2 °F | 94.3 °F | 4.57 in. |
| October | 65.0 °F | 88.4 °F | 2.05 in. |
| November | 55.9 °F | 79.2 °F | 1.01 in. |
| December | 48.7 °F | 71.9 °F | 0.86 in. |
| Annual | 63.4 °F | 86.8 °F | 20.16 in. |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |