Rio Grande City, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 17.4 °C (low) to 30.5 °C (high). Annual precipitation averages 512.1 Millimeters. 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 | 8.7 °C | 21.6 °C | 17.78 mm |
| February | 10.9 °C | 24.3 °C | 19.56 mm |
| March | 14.3 °C | 27.8 °C | 24.13 mm |
| April | 17.9 °C | 31.4 °C | 35.05 mm |
| May | 21.7 °C | 34.3 °C | 68.58 mm |
| June | 23.8 °C | 36.7 °C | 59.94 mm |
| July | 24.4 °C | 37.4 °C | 39.62 mm |
| August | 24.3 °C | 37.7 °C | 31.75 mm |
| September | 22.3 °C | 34.6 °C | 116.08 mm |
| October | 18.3 °C | 31.3 °C | 52.07 mm |
| November | 13.3 °C | 26.2 °C | 25.65 mm |
| December | 9.3 °C | 22.2 °C | 21.84 mm |
| Annual | 17.4 °C | 30.5 °C | 512.05 mm |
| 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 : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |