| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 58°F | 46°F | 2.6" |
| February | 39°F | 64°F | 51°F | 2.0" |
| March | 43°F | 70°F | 56°F | 2.0" |
| April | 46°F | 76°F | 60°F | 1.5" |
| May | 51°F | 84°F | 66°F | 0.3" |
| June | 56°F | 92°F | 73°F | 0.2" |
| July | 59°F | 97°F | 77°F | 0.1" |
| August | 59°F | 95°F | 76°F | 0.1" |
| September | 56°F | 92°F | 72°F | 0.2" |
| October | 49°F | 81°F | 64°F | 0.7" |
| November | 41°F | 68°F | 54°F | 1.2" |
| December | 36°F | 58°F | 47°F | 2.5" |
| Index | Farmington | California | National |
| Air quality index | 45 | 55 | 42 |
| Pollution index | 7,774,440 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 229 |
| Days with moderate air quality | 123 |
| Days w/ poor A.Q. for sensitive groups | 12 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.090% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.050% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Linden, CA | 2,043 | 45 | 10.0% |
| August, CA | 8,046 | 45 | 10.0% |
| Lathrop, CA | 23,863 | 45 | 10.0% |
| Waterloo, CA | 902 | 45 | 10.0% |
| French Camp, CA | 3,641 | 45 | 10.0% |
| Farmington, CA | 169 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Vernon, AZ | 169 | 44 | 12.0% |
| Sisquoc, CA | 169 | 46 | 8.0% |
| Castalia, IA | 169 | 35 | 30.0% |
| Admire, KS | 169 | 22 | 56.0% |
| Westphalia, KS | 169 | 22 | 56.0% |
| Farmington, CA | 169 | 45 | 10.0% |
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