| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 44°F | 70°F | 56°F | 1.6" |
| February | 45°F | 72°F | 57°F | 1.2" |
| March | 47°F | 75°F | 60°F | 0.7" |
| April | 50°F | 78°F | 63°F | 0.5" |
| May | 55°F | 82°F | 66°F | 0.2" |
| June | 59°F | 89°F | 72°F | 0.0" |
| July | 65°F | 94°F | 77°F | 0.2" |
| August | 65°F | 95°F | 78°F | 0.1" |
| September | 63°F | 94°F | 76°F | 0.2" |
| October | 56°F | 85°F | 69°F | 0.2" |
| November | 49°F | 77°F | 62°F | 0.5" |
| December | 44°F | 69°F | 55°F | 1.9" |
| Index | Grand | Riverside | California |
| Air quality index | 89 | 89 | 55 |
| Pollution index | 22,790,900 | 22,790,900 | 10,473,190 |
| 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. |
| Highgrove, CA | 6,201 | 89 | 78.0% |
| Redlands, CA | 71,680 | 89 | 78.0% |
| Norco, CA | 27,021 | 89 | 78.0% |
| Good Hope, CA | 8,431 | 89 | 78.0% |
| El Sobrante, CA | 14,779 | 89 | 78.0% |
| Riverside, CA | 327,569 | 89 | 78.0% |
| City | Population | Air Quality Index | National Avg. |
| Corpus Christi, TX | 326,332 | 42 | 16.0% |
| Santa Ana, CA | 332,610 | 89 | 78.0% |
| Lexington-Fayette, KY | 322,200 | 42 | 16.0% |
| Vaughan, ON | 321,974 | n/a | |
| Stockton, CA | 311,103 | 45 | 10.0% |
| Riverside, CA | 327,569 | 89 | 78.0% |
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