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"Relative humidity" (expressed as a percent) measures water vapor, but RELATIVE to the temperature of the air. In other words, it is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature. As such, relative humidity by itself does not directly indicate the actual amount of water vapor present (definition from National Weather Service). Relative humidity is typically high near the coast, but may be quite low along the foothills. During periods of high temperatures, relative humidity is usually below normal so that discomfort is rare, except for those infrequent periods when high temperatures and high humidities occur simultaneously.
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
|---|---|---|---|---|---|
| January | 60% | 70% | 47% | 52% | 69% |
| February | 58% | 68% | 45% | 50% | 67% |
| March | 61% | 73% | 45% | 51% | 69% |
| April | 61% | 74% | 46% | 52% | 70% |
| May | 66% | 77% | 54% | 57% | 74% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| June | 67% | 79% | 54% | 57% | 76% |
| July | 67% | 80% | 51% | 56% | 77% |
| August | 67% | 80% | 50% | 56% | 77% |
| September | 66% | 79% | 49% | 56% | 76% |
| October | 57% | 68% | 38% | 50% | 69% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| November | 59% | 69% | 43% | 54% | 71% |
| December | 57% | 66% | 43% | 51% | 65% |
| Annual | 62% | 74% | 47% | 54% | 72% |
* Hour of day when measured.
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
|---|---|---|---|---|---|
| January | 65% | 72% | 53% | 64% | 69% |
| February | 65% | 72% | 52% | 63% | 69% |
| March | 67% | 77% | 55% | 64% | 71% |
| April | 69% | 79% | 58% | 65% | 74% |
| May | 73% | 82% | 64% | 69% | 78% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| June | 75% | 83% | 67% | 71% | 81% |
| July | 77% | 86% | 68% | 73% | 84% |
| August | 77% | 85% | 66% | 72% | 84% |
| September | 74% | 83% | 62% | 71% | 80% |
| October | 65% | 73% | 49% | 65% | 73% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| November | 65% | 72% | 47% | 67% | 72% |
| December | 59% | 65% | 44% | 60% | 63% |
| Annual | 70% | 78% | 57% | 67% | 75% |
* Hour of day when measured.
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
|---|---|---|---|---|---|
| January | 67% | 77% | 54% | 55% | 76% |
| February | 64% | 76% | 51% | 52% | 71% |
| March | 64% | 78% | 51% | 50% | 72% |
| April | 64% | 79% | 53% | 49% | 73% |
| May | 67% | 80% | 58% | 56% | 75% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| June | 69% | 81% | 62% | 56% | 77% |
| July | 68% | 82% | 59% | 55% | 78% |
| August | 69% | 83% | 58% | 55% | 78% |
| September | 68% | 82% | 56% | 56% | 77% |
| October | 64% | 78% | 48% | 52% | 76% |
| Month | Daily | 4 A.M.* | 10 A.M.* | 4 P.M.* | 10 P.M.* |
| November | 64% | 76% | 47% | 55% | 74% |
| December | 62% | 73% | 50% | 52% | 71% |
| Annual | 66% | 79% | 54% | 54% | 76% |
* Hour of day when measured.
Source: Western Regional Climate Center
