As the Bay Area approached the summer solstice, the forecast called for the first real heat wave of the summer season. Yes it's summer and yes it gets hot this time of year, but why was the forecast calling for dangerous heat with Heat Advisories and Excessive Heat Warnings? Simply put, strong area of high pressure.

Computer weather models were in agreement depicting building high pressure coupled with developing offshore flow (NE and E winds). As meteorologists we use pattern recognition to predict the weather and we know this pattern is perfect for record heat, similar to the 2006 and 2008 heat events. An Excessive Heat Watch was first issued on June 15 to highlight the upcoming potential for heat risks to sensitive populations . The watch was eventually upgraded to a Heat Advisory. Lastly, the cumulative effect likely took a toll at some locations and the Heat Advisory was finally upgraded to an Excessive Heat Warning for Thursday. It should also be noted that the heat didn't just impact the Central Coast, but much of California and the Desert Southwest. Here is a snapshot of the all heat related hazards issued by the NWS. Locally, the peak heating came in two waves due to strong offshore flow, which led to record warmth on Sunday and near record warmth on Thursday. Except for Sunday, lingering low clouds and patchy fog along the coast kept the coastal areas much cooler. Away from the coast was a completely different story where triple digit highs were common place. The warmest conditions were observed across the interior portions of the North Bay, East Bay and Monterey/San Benito counties. Daytime temperatures were so hot roads and sidewalks buckles. Below is a picture of one such sidewalk. In addition to the dangerous daytime heat, temperatures remained impressively hot at night. Many locations over the higher terrain remained in the 70s and 80s. In fact, one location was still 91 degrees! at 3 AM.

Below are two RERs issued for Record Temperatures
 

RECORD EVENT REPORT
 NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA.
 608 PM PDT SUN JUNE 18 2017
 
 ...NEW RECORD HIGHS ESTABLISHED TODAY JUNE 18, 2017...
 
 LOCATION                    MAX TEMP       PREVIOUS RECORD    
 ---------------------------------------------------------
 KENTFIELD                     103           102 IN 1945
 SAN RAFAEL                    105            98 IN 1962
 SAN FRANCISCO                  88            86 IN 1993 
 SAN FRANCISCO AIRPORT          97            88 IN 1981
 OAKLAND AIRPORT                97            93 IN 1962
 RICHMOND                       92            85 IN 1957
 LIVERMORE                     106           105 IN 1918
 MOFFETT FIELD                 100            95 IN 1993
 SAN JOSE                      103            99 IN 1945                 
 GILROY                        102   (TIED)  102 IN 1981
 
 THE LOW TEMPERATURE FOR THE DAY THUS FAR IN SAN FRANCISCO HAS 
 BEEN 62. IF THIS LOW TEMPERATURE HOLDS FOR THE CALENDAR DAY 
 IT WILL TIE THE RECORD HIGHEST MINIMUM TEMPERATURE SET IN 1993.