| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 48°F | 69°F | 57°F | 2.3" |
| February | 49°F | 69°F | 58°F | 1.9" |
| March | 52°F | 70°F | 60°F | 0.9" |
| April | 54°F | 72°F | 62°F | 0.6" |
| May | 59°F | 73°F | 65°F | 0.3" |
| June | 62°F | 76°F | 67°F | 0.0" |
| July | 66°F | 80°F | 71°F | 0.1" |
| August | 66°F | 82°F | 72°F | 0.0" |
| September | 65°F | 82°F | 72°F | 0.2" |
| October | 60°F | 79°F | 68°F | 0.5" |
| November | 54°F | 75°F | 63°F | 0.7" |
| December | 48°F | 68°F | 57°F | 2.4" |
| Index | Rancho Santa Margarita | California | National |
| Air quality index | 89 | 55 | 42 |
| Pollution index | 44,192,600 | 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 | 0.030% |
| Benzene | 0.280% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.220% |
| Mercury | 0.140% |
| City | Population | Air Quality Index | National Avg. |
| Tustin, CA | 80,815 | 89 | 78.0% |
| Ladera Ranch, CA | 24,996 | 89 | 78.0% |
| San Juan Capistrano, CA | 35,976 | 89 | 78.0% |
| Temescal Valley, CA | 28,420 | 89 | 78.0% |
| Las Flores, CA | 5,089 | 89 | 78.0% |
| Rancho Santa Margarita, CA | 48,280 | 89 | 78.0% |
| City | Population | Air Quality Index | National Avg. |
| Beaumont, CA | 48,272 | 89 | 78.0% |
| La Mirada, CA | 48,260 | 72 | 44.0% |
| Bozeman, MT | 48,330 | 25 | 50.0% |
| Cedar Hill, TX | 48,337 | 51 | 2.0% |
| Ceres, CA | 48,355 | 49 | 2.0% |
| Rancho Santa Margarita, CA | 48,280 | 89 | 78.0% |
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