| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 37°F | 58°F | 46°F | 3.5" |
| February | 40°F | 63°F | 51°F | 3.4" |
| March | 44°F | 68°F | 55°F | 3.2" |
| April | 47°F | 75°F | 60°F | 1.9" |
| May | 52°F | 84°F | 67°F | 0.7" |
| June | 58°F | 93°F | 75°F | 0.4" |
| July | 61°F | 98°F | 78°F | 0.0" |
| August | 59°F | 96°F | 76°F | 0.0" |
| September | 56°F | 92°F | 72°F | 0.2" |
| October | 49°F | 80°F | 63°F | 1.2" |
| November | 42°F | 66°F | 53°F | 2.1" |
| December | 37°F | 57°F | 46°F | 3.6" |
| Index | Williams | California | National |
| Air quality index | 44 | 55 | 42 |
| Pollution index | 2,024,690 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 239 |
| Days with moderate air quality | 124 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Meridian, CA | 278 | 44 | 12.0% |
| Maxwell, CA | 1,256 | 44 | 12.0% |
| College City, CA | 205 | 44 | 12.0% |
| Arbuckle, CA | 3,368 | 44 | 12.0% |
| Colusa, CA | 6,111 | 44 | 12.0% |
| Williams, CA | 5,284 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| West Elgin, ON | 5,284 | n/a | |
| South Amherst, MA | 5,283 | 40 | 20.0% |
| Quantico Base, VA | 5,283 | 47 | 6.0% |
| Glasgow Village, MO | 5,285 | 54 | 8.0% |
| Lindale, GA | 5,282 | 44 | 12.0% |
| Williams, CA | 5,284 | 44 | 12.0% |
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