| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 37°F | 67°F | 51°F | 2.5" |
| February | 38°F | 68°F | 52°F | 1.6" |
| March | 40°F | 73°F | 56°F | 1.1" |
| April | 44°F | 77°F | 59°F | 0.8" |
| May | 50°F | 81°F | 64°F | 0.3" |
| June | 55°F | 90°F | 72°F | 0.0" |
| July | 62°F | 95°F | 77°F | 0.3" |
| August | 61°F | 95°F | 77°F | 0.7" |
| September | 58°F | 93°F | 74°F | 0.2" |
| October | 50°F | 83°F | 65°F | 0.3" |
| November | 41°F | 75°F | 57°F | 0.7" |
| December | 36°F | 66°F | 50°F | 2.9" |
| Index | Winchester | California | National |
| Air quality index | 89 | 55 | 42 |
| Pollution index | 22,790,900 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 42 |
| Days with moderate air quality | 178 |
| Days w/ poor A.Q. for sensitive groups | 79 |
| Days with unhealthy air quality | 58 |
| Pollutant | Total |
| Arsenic | 0.060% |
| Benzene | 0.190% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.220% |
| Mercury | 0.230% |
| City | Population | Air Quality Index | National Avg. |
| French Valley, CA | 39,057 | 89 | 78.0% |
| Canyon Lake, CA | 11,237 | 89 | 78.0% |
| Hemet, CA | 84,686 | 89 | 78.0% |
| Menifee, CA | 92,968 | 89 | 78.0% |
| Warm Springs, CA | 1,445 | 89 | 78.0% |
| Winchester, CA | 2,957 | 89 | 78.0% |
| City | Population | Air Quality Index | National Avg. |
| New Britain, PA | 2,957 | 51 | 2.0% |
| Citrus City, TX | 2,957 | 42 | 16.0% |
| Greensboro, AL | 2,956 | 35 | 30.0% |
| Valley View, PA | 2,956 | 41 | 18.0% |
| Normandin, QC | 2,956 | n/a | |
| Winchester, CA | 2,957 | 89 | 78.0% |
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