Southern California heat wave: How hot will it get? When will it end?

Key Points:

• Southern California is experiencing its worst heat wave of the summer, with Wednesday forecasted as the hottest day, featuring temperatures 10 to 15 degrees above normal and valley highs exceeding 100 degrees.
• Downtown Los Angeles is expected to reach 101 degrees, potentially breaking the daily record of 98 set in 1981, while multiple other locations across the region are predicted to surpass longstanding temperature records.
• The heat wave poses significant health risks due to high temperatures combined with elevated humidity, exacerbated by unusually warm ocean waters and a globally warming climate, with July tying as the warmest on record since 1850.
• Although a slight cooling is anticipated starting Thursday due to Tropical Storm Iselle's remnants, humidity will increase and heat advisories remain in effect through Friday evening, with more substantial cooling expected over the weekend.
• Record-breaking temperatures have already been set earlier in the week at various locations, including downtown Los Angeles, Long Beach Airport, and Camarillo Airport, underscoring the severity of the ongoing heat event.