| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 37°F | 59°F | 46°F | 6.3" |
| February | 41°F | 64°F | 50°F | 4.5" |
| March | 47°F | 70°F | 57°F | 6.1" |
| April | 55°F | 77°F | 65°F | 8.2" |
| May | 62°F | 82°F | 71°F | 8.7" |
| June | 71°F | 91°F | 80°F | 9.1" |
| July | 74°F | 94°F | 83°F | 9.0" |
| August | 74°F | 94°F | 83°F | 8.4" |
| September | 69°F | 91°F | 79°F | 9.7" |
| October | 58°F | 81°F | 68°F | 13.3" |
| November | 47°F | 68°F | 56°F | 7.5" |
| December | 40°F | 60°F | 48°F | 7.9" |
| Index | Rockwall | Texas | National |
| Air quality index | 51 | 52 | 42 |
| Pollution index | 37,723,200 | 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 | 0.060% |
| Benzene | 0.290% |
| Carbon Tetrachloride | 0.220% |
| Lead | 0.230% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Caddo Mills, TX | 1,666 | 51 | 2.0% |
| Josephine, TX | 1,488 | 51 | 2.0% |
| Murphy, TX | 20,711 | 51 | 2.0% |
| Royse City, TX | 13,773 | 51 | 2.0% |
| Forney, TX | 23,871 | 51 | 2.0% |
| Rockwall, TX | 45,168 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Pearl City, HI | 45,159 | 30 | 40.0% |
| Herriman, UT | 45,211 | 51 | 2.0% |
| Cleveland, TN | 45,115 | 1 | 98.0% |
| Lake Ridge, VA | 45,111 | 47 | 6.0% |
| Hilo, HI | 45,248 | 16 | 68.0% |
| Rockwall, TX | 45,168 | 51 | 2.0% |
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