Historic Weekend Rain Gives L.A. & San Diego Wettest July Ever Recorded
On Friday, a raging wildfire burned cars stranded on I-15 near Los Angeles while crews battled drones to put out the flames. On Saturday, part of I-10 collapsed as Los Angeles and San Diego recorded the most rain they’ve ever seen during the month of July. Oh, you know, just another weekend.
What unfolded this weekend was truly a historic event, even if it doesn’t seem like much to most of us in rainier parts of the world. It rains so little during the summer in southern California that it’s unlikely many (if any) people alive right now were around the last time either city saw this much rain in July. Weather records in downtown Los Angeles go back to 1877, and records at San Diego’s Lindbergh Airport go back to 1939 (though the lack of July rain likely extends much earlier than that).
It’s Fire Season
The events that unfolded this weekend were a result of the far-flung gasps of a dying hurricane interrupting the normal, flaming hellscape that is southern California in the summer. Los Angeles recorded 0.32” of rain on Saturday, and San Diego came out on top with just over an inch of rain by sunrise on Sunday. As exciting as it is for us weather nerds, these rainfall totals are paltry when compared to just about everywhere else in the country.
Southern California stays notoriously warm, dry, and windy during the summer months, leading to an often-explosive wildfire season that’s hard to control until the rainy season cranks back up in the fall. The fires this year are on track to be worse than normal due to the lengthy drought that seems like it’s never going to end.
The fires came to national attention on Friday afternoon as an out-of-control wildfire approached a jammed Interstate 15 outside of Los Angeles. Crews rushed to battle the inferno as it lapped at the sides of the highway, but their progress was hindered by some idiots flying drones over the interstate—firefighters were unable to contain the fire in time and it overtook the highway, burning up more than a dozen cars.
Less than 24 hours later, it poured. That’s not normal.
The Flames Are a Dry Heat
You can blame the rain on Hurricane Dolores, a once-powerful storm that reached category four status off the west coast of Mexico before dying a rapid death as it moved into colder waters. Deep, tropical moisture from the storm kept moving north after the storm croaked, pushing its way into California and allowing heavy showers and thunderstorms to develop over the parched countryside.
Such tiny rainfall totals don’t seem like much, but they’re historically significant when you figure that these cities see almost nothing during the dog days of summer. The airports in both Los Angeles and San Diego typically see three one-hundredths of an inch of rain in July. 0.03”. Zero point zero three inches. That’s the amount of most of us can see in one minute during your average heavy thunderstorm.
To put it in perspective, the long-standing weather station at New York’s Central Park averages 133 times more rain than Los Angeles during the month of July. Hey, even Phoenix—which is basically nature’s toaster oven—sees about an inch of rain in an average July thanks to the annual wet monsoon.
Much to the surprise of the many southern Californians on my Facebook feed (and likely yours, as well), the skies opened up over the southern part of the Golden State on Saturday, allowing impressive amounts of rain to fall in short order.
Records Went Down in Flames
LAX recorded 0.32 inches of rain between 7:00 AM Saturday and 7:00 AM Sunday, setting both an all-time one-day rainfall record for the city and an all-time July rainfall record. The previous one-day rainfall record during the month of July was 0.28 inches set back on July 12, 1992. You know the month is dry when five of Los Angeles’ ten wettest July days since 1945 saw little but a cloud sneeze.
The numbers are even more staggering down I-5 in San Diego, where the city’s airport picked up a whopping 1.03 inches of rain. This dwarfs the previous one-day July record of 0.23 inches set back on July 31, 1991. This weekend’s total will push San Diego over the top for the wettest July on record, a title previously held during that wet (“wet”) year of 1991.
Rain is good when you’ve been dry, but a sudden burst of rain in the midst of such a devastating drought is a bad thing. Arid ground has a hard time absorbing water, so when you see heavy rain too quickly, it can overwhelm man-made and natural water infrastructure and create significant flooding.
The flooding was so bad in Desert Center, California—out in the Colorado Desert about 45 minutes east of Indio—that it washed-out a bridge on Interstate 10, sending a vehicle and its occupants plunging more than 15 feet into the wash below. The Desert Sun reports that a pickup truck (pictured above) went down with the bridge as it collapsed; thankfully, the passenger escaped and the driver was rescued with “moderate injuries,” which is to be expected when the road collapses out from underneath you as you’re going down the highway at 70 MPH.
Even as the rain tapers off, flash flooding is possible just about anywhere experiencing heavy rain, and there’s a heightened risk of mud and debris slides in hilly areas, especially spots that recently experienced fires. The risk for landslides can still exist for days after the rain ends, so if you live in an area prone to piles of land casually collapsing, keep an eye out for that.
The rain should come to an end on Monday afternoon, allowing southern California to return to its characteristically sunny, hot, and dry weather. Given the active hurricane season predicted in the eastern Pacific, another incident like this is unlikely but not completely out of the realm of possibility. The rainy season in southern California doesn’t begin until the middle of October, and if this year’s growing El Niño proves its worth, the region could be in for some beneficial rainfall this winter.
[Images: NOAA, Getty Images, Chief Geoff Pemberton/CAL FIRE/Riverside County Fire via AP | Charts/Map: author]