A sweltering heat wave will blanket Southern California through the middle of the week, elevating the fire danger and probably breaking many heat records, according to forecasters. The National Weather Service on Monday issued an excessive-heat warning through Wednesday, saying the high temperatures will create “a dangerous situation” this week. The Antelope Valley and other inland valleys are expected to face the worst heat this week, with triple-digit temperatures. The record books are already being rewritten in places such as Lancaster and Palmdale.