Record-breaking heat as temperatures soared up to 20 degrees above average

SAN DIEGO (FOX 5/KUSI) - Under a Heat Advisory, some areas across Southern California felt record-breaking hot temperatures mid week.

Areas that got record-breaking heat:

Vista
New record: 94
Old record: 90 in 2008
Period of record: 1957

Chula Vista
New record: 94
Old record: 87 in 1921
Period of record: 1918

Escondido
New record: 98
Old record: 96 in 1939
Period of record: 1893

Ramona
New record: 96
Old record: 93 in 2008
Period of record: 1974

Alpine
New record: 93
Old record: 93 in 2007
Period of record: 1951

Campo
New record: 92
Old record: 92 in 2008
Period of record: 1948

Building high pressure and offshore flow allowed for warm and dry conditions to dominate west of the mountains Wednesday, which will be the hottest day of the week.

A Heat Advisory blanketing the inland valleys expired at 7 p.m. Wednesday as onshore flow and the marine layer returns and is expected to cool things down for the second half of the week.

Temperatures will drop about 10 degrees between Wednesday and Thursday afternoon as the ridge of high pressure begins to break down.

Along the coast and coastal valleys, dense fog is likely to develop again and lead to low visibility on the road. Thick fog and visibility less than a mile will likely impact the immediate coast to the 5 freeway. This may also lead to delays once again at the San Diego International Airport.

Halloween daytime highs will be a bit more comfortable with low 70s for the coast, low 80s for valleys, upper 70s for mountains and low 90s for the deserts.

A deeper marine later will persist as a weak coastal eddy spins up in the overnight hours for the next couple of mornings.

Expect stronger onshore flow over the weekend and evening and morning low clouds for the end of the weekend into early next will with a few degrees of cooling.