| 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. |
| Rail Road Flat, CA | 97 | 39 | 22.0% |
| Mi-Wuk Village, CA | 933 | 39 | 22.0% |
| Cedar Ridge, CA | 1,267 | 39 | 22.0% |
| Murphys, CA | 1,944 | 39 | 22.0% |
| Red Corral, CA | 1,557 | 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
10 Best cities in California for employment
Top 10 best public schools in Arnold
Top 10 cities in California with the best education system