Some hikers have ignored the warnings.
SAN DIEGO (KGTV) -- San Diego is bracing for yet another heat wave during a summer proving to be record-breaking.
High pressure will expand across Southern California Monday and Tuesday, bringing high temperatures to the valleys and deserts, according to the National Weather Service.
An Excessive Heat Warning will go into effect Monday morning at 10 a.m. and ends Tuesday night at 8 p.m.
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High temperatures in the lower deserts could reach 110 to 116 with temperatures expected to be between 102 to 110 in the inland empire and 94 to 104 in the mountains.
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Monsoonal moisture is set to return Wednesday into the weekend, bringing some relief from the heat.