City of Irvine
2020 Local Hazard Mitigation Plan
Past Events
Extreme Heat Local data from within Irvine is generally available using the Tustin Irvine Ranch National Weather Service Cooperative Network station. The data indicates that the average maximum temperature for the area from all years between 1902 and 2003 is 85.2°F, occurring in the month of August. 103 Given that the minimum threshold for an extreme heat day in Irvine is 93.2°F, it is rare that the temperature exceeds this threshold on a regular basis. Still, extreme heat events have occurred in the region, which occasionally impact the City as well. Some significant historic extreme heat events include: • In September 1963, the temperature reached 113°F at the now-defunct El Toro Air Force Base, and the surrounding region was hot as well, including coastal areas. Temperatures in Carlsbad and Oceanside reached 108°F. School children and employees were sent home due to the heat, and some agricultural crops were destroyed. • In April 1989, daily high-temperature records were set for all weather monitoring stations in Southern California. Los Angeles and Riverside set records at 106°F and 104°F, respectively. 104
More recent extreme heat events have also affected the greater region surrounding Irvine:
• Throughout July 2018, extreme heat waves occurred throughout Southern California, including Irvine. The hottest day of the heat waves occurred on July 6 when temperatures reached 114°F in Santa Ana, CA. A second but less intense extreme heatwave occurred on July 25, where regional temperatures went above 100°F in places like Burbank. While local temperature data for Irvine is not available, the weather monitoring station at nearby Long Beach Airport indicates that the temperature reached 95°F that day. 105 , 106 • On October 23, 2017, Southern California experienced two extreme heat days. The weather monitoring station at Long Beach Airport indicated that temperatures reached 105°F that day. 107 Heavy Rain Irvine and Orange County have experienced heavy rain events that have inundated many communities. Some significant historical events include: 108 • 1861-1862 - Epic floods caused by rain over 30 days in succession. The Santa Ana River in Anaheim ran 4’ deep and spread in an unbroken sheet to Coyote Hills, 3 miles beyond (present Fullerton). Twenty people died in Orange County due to this event. • 1997 - A stationary line of thunderstorms brought the heaviest rain in 70 years to portions of Orange County. Rainfall totals ranged from 4 inches to 10 inches in some parts of the southland. Newport Beach and Laguna Beach reported respective rainfall totals of 6.00 inches and 5.50 inches, both all-time records for a single day by more than an inch. Widespread flooding in Orange County. Mudslides and coastal erosion. • 1998 - Up to 3” of rainfall fell over Southern California, causing catastrophic and widespread flooding, especially in Newport Beach and Irvine. Significant property damage occurred in south Orange County, requiring evacuations and swift water rescues. Impacts from this event included landslides, mudslides, sinkholes, and damage to roads, bridges, and railroads.
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