| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 60°F | 46°F | 6.0" |
| February | 39°F | 64°F | 50°F | 5.7" |
| March | 41°F | 67°F | 52°F | 4.6" |
| April | 43°F | 71°F | 55°F | 2.4" |
| May | 46°F | 77°F | 60°F | 1.1" |
| June | 50°F | 83°F | 64°F | 0.4" |
| July | 52°F | 85°F | 65°F | 0.0" |
| August | 52°F | 84°F | 64°F | 0.0" |
| September | 49°F | 85°F | 64°F | 0.2" |
| October | 46°F | 78°F | 59°F | 2.0" |
| November | 41°F | 67°F | 52°F | 3.2" |
| December | 36°F | 59°F | 46°F | 6.9" |
| Index | Penngrove | California | National |
| Air quality index | 34 | 55 | 42 |
| Pollution index | 7,898,290 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 346 |
| Days with moderate air quality | 18 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.260% |
| Benzene | 0.080% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.240% |
| Mercury | 0.270% |
| City | Population | Air Quality Index | National Avg. |
| Glen Ellen, CA | 1,214 | 34 | 32.0% |
| Petaluma, CA | 60,865 | 34 | 32.0% |
| St. Helena, CA | 6,049 | 34 | 32.0% |
| Bloomfield, CA | 243 | 34 | 32.0% |
| Point Reyes Station, CA | 210 | 34 | 32.0% |
| Penngrove, CA | 2,368 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Grissom AFB, IN | 2,368 | 37 | 26.0% |
| Konterra, MD | 2,368 | 47 | 6.0% |
| Warsaw, VA | 2,368 | 44 | 12.0% |
| Holcomb, KS | 2,367 | 15 | 70.0% |
| Wells, MN | 2,367 | 15 | 70.0% |
| Penngrove, CA | 2,368 | 34 | 32.0% |
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