Scattered low cloud and dense fog are expected to erode rapidly toward the San Diego County coast on Saturday, the National Weather Service said.
Warming conditions were likely through early next week, with highs reaching 5 to 12 degrees above normal by Sunday.
Subtle increases in humidity aloft are expected to lead to increased mid-level cloud cover and a slight chance of showers and isolated thunderstorms in the southern mountains and lower deserts on Monday.
Cooler conditions will develop late next week, forecasters said.
On Friday, the NWS said Escondido and El Cajon tied the highest minimum temperature records, both at 65 degrees.
High temperatures along the coast on Saturday are forecast to be 73 to 78 degrees with overnight lows of 59 to 64. Highs in the western valleys are forecast to be 86 to 91 and 94 to 99 near the foothills with overnight lows of 61 to 67. Highs in the mountains were expected to be 90 to 98 with overnight lows of 60 to 70, and highs in the deserts were expected to be 110 to 115 with overnight lows of 77 to 85.
Hot, dry weather was expected early next week inland, while sea breezes moderate coastal areas daily.
Some increase in humidity was expected by Monday, but it will likely remain quite warm, with gusty winds late in the day and evening below the passes and canyons. The chance of thunderstorms was very low on Monday and Tuesday, but could bring some dry lightning.
Temperatures are expected to be above average through the middle of the week, then return to around average on Thursday and continue to fall over the July 4 holiday weekend.
The combination of afternoon heat, gusty winds and low humidity was expected to keep fiery weather conditions high on the desert mountain slopes and in the deserts for a few hours each day.