| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 57°F | 45°F | 2.0" |
| February | 39°F | 61°F | 48°F | 1.5" |
| March | 47°F | 70°F | 57°F | 3.0" |
| April | 55°F | 77°F | 64°F | 3.5" |
| May | 62°F | 82°F | 71°F | 4.1" |
| June | 71°F | 91°F | 80°F | 3.1" |
| July | 74°F | 94°F | 84°F | 2.8" |
| August | 74°F | 95°F | 84°F | 2.2" |
| September | 67°F | 87°F | 76°F | 2.3" |
| October | 56°F | 78°F | 66°F | 2.9" |
| November | 47°F | 67°F | 56°F | 2.0" |
| December | 38°F | 57°F | 46°F | 1.7" |
| Index | Decatur | Texas | National |
| Air quality index | 33 | 52 | 42 |
| Pollution index | 1,399,310 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 329 |
| Days with moderate air quality | 33 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.010% |
| Mercury | 0.002% |
| City | Population | Air Quality Index | National Avg. |
| Chico, TX | 1,166 | 26 | 48.0% |
| Alvord, TX | 1,104 | 26 | 48.0% |
| Boyd, TX | 1,375 | 33 | 34.0% |
| Bridgeport, TX | 6,498 | 33 | 34.0% |
| Aurora, TX | 1,497 | 33 | 34.0% |
| Decatur, TX | 6,976 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Benton, IL | 6,977 | 43 | 14.0% |
| Milltown, NJ | 6,973 | 41 | 18.0% |
| Oak Ridge, NC | 6,979 | 43 | 14.0% |
| Chatsworth, ON | 6,972 | n/a | |
| Old Greenwich, CT | 6,980 | 43 | 14.0% |
| Decatur, TX | 6,976 | 33 | 34.0% |
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