| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 35°F | 54°F | 44°F | 11.6" |
| February | 39°F | 60°F | 49°F | 2.6" |
| March | 48°F | 70°F | 58°F | 6.5" |
| April | 51°F | 73°F | 62°F | 5.8" |
| May | 63°F | 81°F | 71°F | 8.0" |
| June | 70°F | 90°F | 79°F | 11.0" |
| July | 71°F | 92°F | 80°F | 4.1" |
| August | 73°F | 96°F | 83°F | 1.9" |
| September | 67°F | 91°F | 78°F | 4.9" |
| October | 54°F | 80°F | 66°F | 6.8" |
| November | 47°F | 70°F | 58°F | 4.2" |
| December | 34°F | 60°F | 46°F | 5.3" |
| Index | Allen | Texas | National |
| Air quality index | 51 | 52 | 42 |
| Pollution index | 8,884,190 | 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 | 0.030% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.040% |
| Lead | 0.260% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Rowlett, TX | 65,426 | 51 | 2.0% |
| Fairview, TX | 8,998 | 51 | 2.0% |
| Little Elm, TX | 49,792 | 51 | 2.0% |
| New Hope, TX | 600 | 51 | 2.0% |
| St. Paul CDP, TX | 594 | 51 | 2.0% |
| Allen, TX | 104,040 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| San Mateo, CA | 103,619 | 43 | 14.0% |
| Green Bay, WI | 104,508 | 36 | 28.0% |
| Norwalk, CA | 104,524 | 72 | 44.0% |
| Rialto, CA | 103,549 | 89 | 78.0% |
| Wichita Falls, TX | 104,657 | 26 | 48.0% |
| Allen, TX | 104,040 | 51 | 2.0% |
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