| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 58°F | 46°F | 2.7" |
| February | 40°F | 63°F | 50°F | 1.5" |
| March | 48°F | 70°F | 58°F | 2.6" |
| April | 55°F | 77°F | 65°F | 4.3" |
| May | 62°F | 83°F | 72°F | 4.7" |
| June | 71°F | 92°F | 81°F | 3.7" |
| July | 73°F | 95°F | 83°F | 2.0" |
| August | 73°F | 97°F | 84°F | 1.8" |
| September | 67°F | 90°F | 77°F | 3.0" |
| October | 56°F | 80°F | 66°F | 2.3" |
| November | 47°F | 68°F | 56°F | 2.4" |
| December | 39°F | 59°F | 47°F | 1.7" |
| Index | Ovilla | Texas | National |
| Air quality index | 51 | 52 | 42 |
| Pollution index | 3,706,540 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 181 |
| Days with moderate air quality | 155 |
| Days w/ poor A.Q. for sensitive groups | 28 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.040% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Ennis, TX | 19,917 | 41 | 18.0% |
| Garrett, TX | 924 | 41 | 18.0% |
| Pecan Hill, TX | 570 | 51 | 2.0% |
| Cockrell Hill, TX | 4,200 | 51 | 2.0% |
| DeSoto, TX | 53,170 | 51 | 2.0% |
| Ovilla, TX | 4,010 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Shackle Island, TN | 4,010 | 45 | 10.0% |
| Esparto, CA | 4,009 | 35 | 30.0% |
| Nassau Bay, TX | 4,009 | 52 | 4.0% |
| Gardnertown, NY | 4,011 | 36 | 28.0% |
| Greencastle, PA | 4,008 | 40 | 20.0% |
| Ovilla, TX | 4,010 | 51 | 2.0% |
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