| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 31°F | 23°F | 2.8" |
| February | 14°F | 32°F | 23°F | 2.1" |
| March | 23°F | 43°F | 32°F | 3.0" |
| April | 33°F | 58°F | 45°F | 3.5" |
| May | 43°F | 68°F | 55°F | 4.4" |
| June | 51°F | 75°F | 63°F | 5.3" |
| July | 55°F | 79°F | 67°F | 4.7" |
| August | 53°F | 77°F | 65°F | 5.0" |
| September | 47°F | 71°F | 59°F | 3.4" |
| October | 39°F | 59°F | 48°F | 4.9" |
| November | 29°F | 47°F | 38°F | 3.0" |
| December | 22°F | 35°F | 28°F | 3.5" |
| Index | Olean | New York | National |
| Air quality index | 9 | 43 | 42 |
| Pollution index | 2,885,140 | 6,179,275 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 357 |
| Days with moderate air quality | 6 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.010% |
| Mercury | 0.002% |
| City | Population | Air Quality Index | National Avg. |
| Weston Mills, NY | 1,297 | 9 | 82.0% |
| Limestone, NY | 458 | 9 | 82.0% |
| Bradford, PA | 8,284 | 9 | 82.0% |
| Foster Brook, PA | 1,115 | 9 | 82.0% |
| Lewis Run, PA | 732 | 9 | 82.0% |
| Olean, NY | 13,580 | 9 | 82.0% |
| City | Population | Air Quality Index | National Avg. |
| Jasper, AL | 13,584 | 53 | 6.0% |
| Roselle Park, NJ | 13,574 | 51 | 2.0% |
| South Glengarry, ON | 13,573 | n/a | |
| Iona, FL | 13,588 | 36 | 28.0% |
| Oatfield, OR | 13,588 | 38 | 24.0% |
| Olean, NY | 13,580 | 9 | 82.0% |
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