| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 46°F | 29°F | 6.9" |
| February | 20°F | 52°F | 35°F | 9.4" |
| March | 24°F | 58°F | 40°F | 3.0" |
| April | 26°F | 60°F | 43°F | 3.9" |
| May | 31°F | 68°F | 49°F | 3.6" |
| June | 38°F | 80°F | 60°F | 1.4" |
| July | 43°F | 85°F | 65°F | 2.1" |
| August | 40°F | 83°F | 63°F | 2.0" |
| September | 35°F | 77°F | 56°F | 2.2" |
| October | 28°F | 67°F | 46°F | 4.3" |
| November | 19°F | 55°F | 35°F | 2.6" |
| December | 15°F | 47°F | 29°F | 5.7" |
| Index | Arnold | California | National |
| Air quality index | 39 | 55 | 42 |
| Pollution index | 1,641,280 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 331 |
| Days with moderate air quality | 33 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.090% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.020% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Red Corral, CA | 1,557 | 39 | 22.0% |
| Sierra Village, CA | 226 | 39 | 22.0% |
| Dorrington, CA | 407 | 39 | 22.0% |
| Twain Harte, CA | 2,502 | 39 | 22.0% |
| Buckhorn, CA | 2,175 | 39 | 22.0% |
| Arnold, CA | 2,099 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Gurdon, AR | 2,099 | 32 | 36.0% |
| Oakland, MD | 2,099 | 36 | 28.0% |
| Hoyt Lakes, MN | 2,099 | 35 | 30.0% |
| Choctaw Lake, OH | 2,099 | 45 | 10.0% |
| Winnsboro Mills, SC | 2,099 | 43 | 14.0% |
| Arnold, CA | 2,099 | 39 | 22.0% |
Here are the best places to live in California
See the best places to live in Arnold
Most Dangerous Cities In The US
These are the 10 cheapest cities in California