LOS ANGELES, CA — A mild Fourth of July holiday is expected to give way to record-setting heat across Los Angeles by the end of the week, the National Weather Service warned Monday.

- emperatures will reach dangerous levels in much of Southern California, starting Thursday. Scorching temperatures could go as high as 112 in some pats of the San Fernando Valley, 108 in the San Gabriel Valley, and 90 at the beaches. ``A strong upper level high pressure system is forecast to expand westward from the Central United States later this week, causing heat to build significantly across Southwestern California,'' according to an NWS statement.

The NWS said a fairly deep marine layer and onshore flow will keep temperatures near or below normal across most of the region through Independence Day. On the 4th of July, the high in Hollywood is expected to be 80 degrees, 86 degrees in Woodland Hills, 85 degrees in Pasadena, and 68 degrees in Venice. But on Thursday, the atmosphere will begin to warm, the marine layer will become more shallow, and onshore flow will decrease.



``... The combination of gusty winds, high temperatures and low relative humidity will increase fire danger substantially, possibly approaching critical levels,'' according to the statement.

On Friday and Saturday, high temperatures will likely be between 100 and 112 degrees in many valley locations, in the mountains at lower elevations, and in the Antelope Valley. Many daily high temperature records are likely to be broken both days.

``The very high daytime temperatures and limited overnight cooling will create significant heat stress for people in the region. If computer models, which have been consistent, continue to show this event unfolding as is, Excessive Heat Watches will likely have to be issued for a good portion of the region, and Heat Advisories may be needed in most other areas,'' the NWS warned. ``People should plan to reduce time in the sun during peak heating hours later this week into this weekend and drink additional water to keep hydrated.''