| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 39°F | 58°F | 48°F | 3.3" |
| February | 43°F | 62°F | 52°F | 3.0" |
| March | 45°F | 67°F | 54°F | 1.8" |
| April | 47°F | 71°F | 57°F | 1.9" |
| May | 52°F | 78°F | 63°F | 0.6" |
| June | 56°F | 85°F | 68°F | 0.0" |
| July | 58°F | 90°F | 71°F | 0.0" |
| August | 57°F | 90°F | 70°F | 0.0" |
| September | 56°F | 86°F | 68°F | 0.0" |
| October | 50°F | 77°F | 62°F | 1.4" |
| November | 45°F | 68°F | 55°F | 1.2" |
| December | 40°F | 57°F | 47°F | 2.3" |
| Index | Hercules | California | National |
| Air quality index | 40 | 55 | 42 |
| Pollution index | 19,202,400 | 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 | 0.180% |
| Benzene | 0.140% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.280% |
| Mercury | 0.060% |
| City | Population | Air Quality Index | National Avg. |
| Sausalito, CA | 7,177 | 40 | 20.0% |
| Tiburon, CA | 9,167 | 40 | 20.0% |
| Crockett, CA | 3,205 | 40 | 20.0% |
| Albany, CA | 20,145 | 40 | 20.0% |
| El Cerrito CDP, CA | 5,699 | 40 | 20.0% |
| Hercules, CA | 26,090 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Neenah, WI | 26,083 | 37 | 26.0% |
| Milford, MA | 26,072 | 40 | 20.0% |
| Wethersfield, CT | 26,068 | 41 | 18.0% |
| Bessemer, AL | 26,063 | 53 | 6.0% |
| West Odessa, TX | 26,117 | 28 | 44.0% |
| Hercules, CA | 26,090 | 40 | 20.0% |
Here are the best places to live in California
See the best places to live in Hercules
These are the largest cities in California
These are the 10 cheapest cities in California