| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 46°F | 34°F | 7.1" |
| February | 30°F | 53°F | 40°F | 2.7" |
| March | 41°F | 68°F | 53°F | 9.2" |
| April | 46°F | 70°F | 57°F | 4.5" |
| May | 57°F | 80°F | 68°F | 8.4" |
| June | 66°F | 87°F | 76°F | 8.7" |
| July | 68°F | 91°F | 79°F | 6.8" |
| August | 70°F | 95°F | 81°F | 7.0" |
| September | 62°F | 87°F | 73°F | 4.9" |
| October | 49°F | 75°F | 60°F | 5.0" |
| November | 36°F | 66°F | 50°F | 3.0" |
| December | 24°F | 49°F | 35°F | 3.1" |
| Index | Delaware | Oklahoma | National |
| Air quality index | 38 | 55 | 42 |
| Pollution index | 261,723 | 1,271,533 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 289 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.003% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lenapah, OK | 356 | 38 | 24.0% |
| South Coffeyville, OK | 828 | 38 | 24.0% |
| Wann, OK | 144 | 38 | 24.0% |
| New Alluwe, OK | 62 | 38 | 24.0% |
| Nowata, OK | 3,673 | 45 | 10.0% |
| Delaware, OK | 388 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Beckwourth, CA | 388 | 46 | 8.0% |
| Nipinnawasee, CA | 388 | 50 | = 100 |
| Columbus City, IA | 388 | 32 | 36.0% |
| Miles, IA | 388 | 42 | 16.0% |
| Tenkiller, OK | 388 | 36 | 28.0% |
| Delaware, OK | 388 | 38 | 24.0% |
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