| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 41°F | 59°F | 50°F | 2.8" |
| February | 45°F | 62°F | 53°F | 3.1" |
| March | 47°F | 65°F | 55°F | 2.9" |
| April | 49°F | 67°F | 57°F | 1.8" |
| May | 52°F | 69°F | 59°F | 0.4" |
| June | 54°F | 72°F | 62°F | 0.3" |
| July | 56°F | 73°F | 63°F | 0.0" |
| August | 57°F | 73°F | 63°F | 0.0" |
| September | 55°F | 76°F | 64°F | 0.1" |
| October | 52°F | 73°F | 61°F | 1.0" |
| November | 47°F | 65°F | 56°F | 1.9" |
| December | 42°F | 59°F | 50°F | 4.1" |
| Index | Alto | California | National |
| Air quality index | 40 | 55 | 42 |
| Pollution index | 8,232,360 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 290 |
| Days with moderate air quality | 74 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Alameda, CA | 79,827 | 40 | 20.0% |
| Oakland, CA | 422,575 | 40 | 20.0% |
| Corte Madera, CA | 9,793 | 40 | 20.0% |
| Mill Valley, CA | 14,456 | 40 | 20.0% |
| Strawberry, CA | 5,325 | 40 | 20.0% |
| Alto, CA | 818 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Maricopa Colony, AZ | 818 | 74 | 48.0% |
| Enterprise, KS | 818 | 32 | 36.0% |
| Village of Clarkston, MI | 818 | 38 | 24.0% |
| Woodridge, NY | 818 | 36 | 28.0% |
| Woodsburgh, NY | 818 | 51 | 2.0% |
| Alto, CA | 818 | 40 | 20.0% |
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