| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 39°F | 63°F | 49°F | 3.3" |
| February | 43°F | 67°F | 53°F | 1.7" |
| March | 51°F | 74°F | 61°F | 4.5" |
| April | 58°F | 81°F | 68°F | 3.2" |
| May | 65°F | 86°F | 74°F | 4.7" |
| June | 72°F | 92°F | 81°F | 2.2" |
| July | 74°F | 96°F | 84°F | 1.3" |
| August | 73°F | 96°F | 84°F | 2.8" |
| September | 68°F | 91°F | 78°F | 4.7" |
| October | 57°F | 82°F | 68°F | 4.5" |
| November | 49°F | 73°F | 59°F | 3.7" |
| December | 42°F | 64°F | 51°F | 2.8" |
| Index | Calvert | Texas | National |
| Air quality index | 38 | 52 | 42 |
| Pollution index | 402,930 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 329 |
| Days with moderate air quality | 36 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Hearne, TX | 4,421 | 38 | 24.0% |
| Bremond, TX | 981 | 38 | 24.0% |
| Franklin, TX | 1,585 | 38 | 24.0% |
| Calvert, TX | 1,479 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Salem, NC | 1,479 | 43 | 14.0% |
| Grand Ronde, OR | 1,479 | 32 | 36.0% |
| Carrizo Hill, TX | 1,479 | 25 | 50.0% |
| Strong, ON | 1,479 | n/a | |
| Akron, IA | 1,478 | 35 | 30.0% |
| Calvert, TX | 1,479 | 38 | 24.0% |
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