| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 38°F | 58°F | 46°F | 4.2" |
| February | 40°F | 64°F | 51°F | 3.7" |
| March | 44°F | 71°F | 56°F | 3.5" |
| April | 48°F | 76°F | 61°F | 4.2" |
| May | 54°F | 86°F | 69°F | 1.1" |
| June | 60°F | 94°F | 77°F | 3.0" |
| July | 65°F | 98°F | 81°F | 0.5" |
| August | 63°F | 97°F | 79°F | 0.2" |
| September | 58°F | 93°F | 74°F | 2.3" |
| October | 50°F | 81°F | 64°F | 4.6" |
| November | 42°F | 68°F | 53°F | 3.1" |
| December | 36°F | 58°F | 45°F | 5.6" |
| Index | Hartland | California | National |
| Air quality index | 66 | 55 | 42 |
| Pollution index | 2,235,730 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 127 |
| Days with moderate air quality | 157 |
| Days w/ poor A.Q. for sensitive groups | 78 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.030% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Wilsonia, CA | 0 | 66 | 32.0% |
| Seville, CA | 449 | 66 | 32.0% |
| Hartland, CA | 0 | 66 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Chase, AK | 0 | 31 | 38.0% |
| Chiniak, AK | 0 | 31 | 38.0% |
| Chisana, AK | 0 | 31 | 38.0% |
| Dot Lake, AK | 0 | 38 | 24.0% |
| Eureka Roadhouse, AK | 0 | 31 | 38.0% |
| Hartland, CA | 0 | 66 | 32.0% |
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