| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 40°F | 62°F | 50°F | 3.1" |
| February | 44°F | 68°F | 55°F | 1.6" |
| March | 51°F | 74°F | 62°F | 5.0" |
| April | 59°F | 81°F | 69°F | 3.3" |
| May | 65°F | 86°F | 75°F | 5.5" |
| June | 73°F | 94°F | 83°F | 2.9" |
| July | 76°F | 96°F | 85°F | 1.9" |
| August | 76°F | 98°F | 87°F | 1.5" |
| September | 70°F | 92°F | 80°F | 3.6" |
| October | 60°F | 83°F | 70°F | 4.3" |
| November | 50°F | 72°F | 60°F | 1.4" |
| December | 42°F | 64°F | 51°F | 1.8" |
| Index | Killeen | Texas | National |
| Air quality index | 42 | 52 | 42 |
| Pollution index | 798,696 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 284 |
| Days with moderate air quality | 79 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Copperas Cove, TX | 32,960 | 42 | 16.0% |
| Kempner, TX | 1,057 | 42 | 16.0% |
| Fort Hood, TX | 23,302 | 42 | 16.0% |
| Salado, TX | 2,848 | 42 | 16.0% |
| Harker Heights, TX | 31,657 | 42 | 16.0% |
| Killeen, TX | 148,573 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Guelph, ON | 147,931 | n/a | |
| Lévis, QC | 149,331 | n/a | |
| Naperville, IL | 147,734 | 55 | 10.0% |
| Rockford, IL | 147,441 | 42 | 16.0% |
| Joliet, IL | 147,323 | 55 | 10.0% |
| Killeen, TX | 148,573 | 42 | 16.0% |
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