| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 30°F | 21°F | 0.8" |
| February | 14°F | 34°F | 23°F | 1.0" |
| March | 28°F | 49°F | 37°F | 2.2" |
| April | 39°F | 63°F | 49°F | 4.1" |
| May | 49°F | 73°F | 60°F | 5.2" |
| June | 60°F | 83°F | 71°F | 7.1" |
| July | 64°F | 86°F | 75°F | 4.2" |
| August | 62°F | 83°F | 71°F | 5.5" |
| September | 53°F | 77°F | 63°F | 2.8" |
| October | 41°F | 64°F | 51°F | 4.0" |
| November | 28°F | 49°F | 38°F | 3.7" |
| December | 16°F | 33°F | 24°F | 2.5" |
| Index | Marcus | Iowa | National |
| Air quality index | 41 | 39 | 50 |
| Pollution index | 890,079 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 254 |
| Days with moderate air quality | 110 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.004% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Alton, IA | 1,325 | 41 | 18% |
| Granville, IA | 362 | 41 | 18% |
| Oyens, IA | 88 | 41 | 18% |
| Calumet, IA | 192 | 41 | 18% |
| Larrabee, IA | 202 | 41 | 18% |
| Marcus, IA | 1,146 | 41 | 18% |
| City, State | Population | Air Quality Index | National Avg. |
| Rome City, IN | 1,146 | 47 | 6% |
| Summerland, CA | 1,146 | 44 | 12% |
| Edison, GA | 1,146 | 43 | 14% |
| Plattekill, NY | 1,146 | 36 | 28% |
| Kersey, PA | 1,146 | 33 | 34% |
| Marcus, IA | 1,146 | 41 | 18% |