| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 27°F | 45°F | 35°F | 4.8" |
| February | 28°F | 47°F | 36°F | 6.4" |
| March | 36°F | 57°F | 46°F | 6.0" |
| April | 45°F | 68°F | 56°F | 6.7" |
| May | 55°F | 76°F | 65°F | 6.5" |
| June | 64°F | 84°F | 74°F | 8.6" |
| July | 68°F | 88°F | 78°F | 8.7" |
| August | 66°F | 86°F | 76°F | 7.5" |
| September | 60°F | 80°F | 69°F | 8.6" |
| October | 49°F | 69°F | 58°F | 8.1" |
| November | 38°F | 58°F | 47°F | 7.5" |
| December | 32°F | 50°F | 40°F | 7.1" |
| Index | Walker Mill | Maryland | National |
| Air quality index | 47 | 43 | 42 |
| Pollution index | 849,185 | 5,342,367 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 209 |
| Days with moderate air quality | 145 |
| Days w/ poor A.Q. for sensitive groups | 10 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Odenton, MD | 43,210 | 46 | 8.0% |
| Gambrills, MD | 3,011 | 46 | 8.0% |
| New Carrollton, MD | 13,268 | 47 | 6.0% |
| Silver Hill, MD | 5,346 | 47 | 6.0% |
| Aspen Hill, MD | 55,715 | 47 | 6.0% |
| Walker Mill, MD | 10,032 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Mayfield, KY | 10,031 | 44 | 12.0% |
| Oil City, PA | 10,033 | 9 | 82.0% |
| Uniontown, PA | 10,028 | 36 | 28.0% |
| Richmond Heights, FL | 10,026 | 41 | 18.0% |
| Hamburg, NY | 10,025 | 39 | 22.0% |
| Walker Mill, MD | 10,032 | 47 | 6.0% |