| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 10°F | 26°F | 17°F | 1.7" |
| February | 12°F | 28°F | 20°F | 2.1" |
| March | 27°F | 46°F | 35°F | 4.7" |
| April | 37°F | 60°F | 47°F | 3.8" |
| May | 50°F | 72°F | 60°F | 8.6" |
| June | 60°F | 82°F | 71°F | 4.7" |
| July | 63°F | 84°F | 73°F | 3.8" |
| August | 60°F | 80°F | 70°F | 9.3" |
| September | 53°F | 78°F | 64°F | 8.0" |
| October | 42°F | 64°F | 52°F | 5.7" |
| November | 26°F | 47°F | 35°F | 5.0" |
| December | 9°F | 24°F | 17°F | 1.2" |
| Index | Armstrong | Iowa | National |
| Air quality index | 15 | 39 | 42 |
| Pollution index | 1,155,680 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 118 |
| Days with good air quality | 118 |
| Days with moderate air quality | 0 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Ringsted, IA | 472 | 15 | 70.0% |
| Graettinger, IA | 1,044 | 15 | 70.0% |
| Bancroft, IA | 719 | 15 | 70.0% |
| Swea City, IA | 639 | 15 | 70.0% |
| Lone Rock, IA | 179 | 15 | 70.0% |
| Armstrong, IA | 846 | 15 | 70.0% |
| City | Population | Air Quality Index | National Avg. |
| Rosedale, IN | 846 | 45 | 10.0% |
| Eden, MD | 846 | 36 | 28.0% |
| Baroda, MI | 846 | 39 | 22.0% |
| Courtland, MS | 846 | 33 | 34.0% |
| Webequie, ON | 846 | n/a | |
| Armstrong, IA | 846 | 15 | 70.0% |
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