Hot conditions were expected over the next several days in San Diego County as high pressure builds across the western United States, the National Weather Service said Sunday.
A heat advisory was issued by the NWS from 10 a.m. Sunday to 8 p.m. Monday for San Diego County valleys.
Above-average temperatures, low afternoon relative humidity and gusty winds could lead to several hours of elevated fire weather conditions on the desert mountain slopes and into the deserts late Sunday and Monday.
High temperatures along the coast Sunday were predicted to be 73 to 78 degrees with overnight lows of 60 to 65. Highs in the western valleys were expected to be 87 to 92, and 96 to 101 near the foothills with overnight lows of 62 to 68. Highs in the mountains were expected to be 90 to 97 with overnight lows of 62 to 70, and highs in the deserts were predicted to be 108 to 113 with overnight lows of 76 to 83.
Monsoonal moisture may begin to filter into the deserts Sunday afternoon, with a deeper surge expected on Monday, forecasters said.
Weak easterly waves moving along the southwestern coast might lead to widespread shower and thunderstorm activity to the east of the San Diego County area, though some isolated activity may develop across the mountains and deserts during peak heat hours each afternoon Monday into the middle of the week.
Most areas were likely to see some cumulus clouds, though dry lightning is possible with thunderstorm development.
Patchy fog with visibility down to 1 nautical mile was possible over the coastal waters Monday and Tuesday morning. Otherwise, no hazardous marine weather was expected through Thursday.