| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 42°F | 58°F | 50°F | 3.5" |
| February | 46°F | 61°F | 53°F | 3.3" |
| March | 46°F | 64°F | 54°F | 2.6" |
| April | 48°F | 66°F | 56°F | 1.8" |
| May | 52°F | 69°F | 59°F | 0.6" |
| June | 56°F | 73°F | 62°F | 0.1" |
| July | 57°F | 75°F | 64°F | 0.0" |
| August | 58°F | 76°F | 64°F | 0.0" |
| September | 57°F | 76°F | 64°F | 0.2" |
| October | 53°F | 72°F | 61°F | 1.4" |
| November | 48°F | 66°F | 56°F | 1.3" |
| December | 42°F | 58°F | 49°F | 3.2" |
| Index | Castro Valley | California | National |
| Air quality index | 40 | 55 | 50 |
| Pollution index | 6,427,290 | 18,106,726 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 290 |
| Days with moderate air quality | 74 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.110% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.003% |
| City, State | Population | Air Quality Index | National Avg. |
| San Lorenzo, CA | 24,790 | 40 | 20% |
| Alameda, CA | 77,409 | 40 | 20% |
| Oakland, CA | 412,040 | 40 | 20% |
| Albany, CA | 19,420 | 40 | 20% |
| Kensington, CA | 5,602 | 40 | 20% |
| Castro Valley, CA | 62,825 | 40 | 20% |
| City, State | Population | Air Quality Index | National Avg. |
| Bowling Green, KY | 62,824 | 43 | 14% |
| Greenville, SC | 62,776 | 46 | 8% |
| Cheyenne, WY | 62,879 | 43 | 14% |
| South Jordan, UT | 62,751 | 51 | 2% |
| Waltham, MA | 62,699 | 43 | 14% |
| Castro Valley, CA | 62,825 | 40 | 20% |
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