| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 58°F | 45°F | 5.2" |
| February | 39°F | 62°F | 49°F | 4.8" |
| March | 48°F | 70°F | 58°F | 3.6" |
| April | 55°F | 77°F | 65°F | 3.9" |
| May | 62°F | 83°F | 72°F | 8.5" |
| June | 71°F | 92°F | 81°F | 6.3" |
| July | 73°F | 95°F | 83°F | 4.0" |
| August | 73°F | 96°F | 84°F | 4.1" |
| September | 66°F | 89°F | 77°F | 2.2" |
| October | 55°F | 80°F | 66°F | 4.6" |
| November | 47°F | 68°F | 56°F | 3.4" |
| December | 38°F | 58°F | 47°F | 7.0" |
| Index | Forney | 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. |
| Sunnyvale, TX | 6,664 | 51 | 2.0% |
| Heath, TX | 9,069 | 51 | 2.0% |
| Rowlett, TX | 65,426 | 51 | 2.0% |
| Crandall, TX | 3,848 | 51 | 2.0% |
| Post Oak Bend City, TX | 515 | 51 | 2.0% |
| Forney, TX | 23,871 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Lathrop, CA | 23,863 | 45 | 10.0% |
| Faribault, MN | 23,853 | 37 | 26.0% |
| Columbus, MS | 23,853 | 35 | 30.0% |
| Calabasas, CA | 23,842 | 72 | 44.0% |
| Saginaw, TX | 23,835 | 51 | 2.0% |
| Forney, TX | 23,871 | 51 | 2.0% |
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