A surge of tropical moisture pushed into central California from the south on June 17 and 18. This moisture moved into an unstable airmass as temperatures were much warmer than normal across the area.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HNX wrote it up.
A surge of tropical moisture pushed into central California from the south on June 17 and 18. This moisture moved into an unstable airmass as temperatures were much warmer than normal across the area. As a result, some thunderstorms broke out over the Kern County Mountains and Deserts and the Sierra Nevada during the afternoon of June 17; and over the San Joaquin Valley during the late evening of June 17 and early morning of June 18. While precipitation amounts were light (anywhere from trace amounts to a tenth of an inch), the thunderstorms produced some strong outflow gusts which resulted in some wind damage as trees that were weakened or killed by drought conditions were toppled by the strong wind gusts.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at Jun 17, 3:53 PM PST, 9 hours 44 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Hanford CA 453 PM PDT Thu Jun 17 2021 Updated Air Quality Issues section .SYNOPSIS... Dangerously hot conditions will continue across the area through the weekend as a large area of high pressure remains over the region. Mid-level moisture moving around the ridge will bring isolated showers and thunderstorms mainly over the high Sierra through Friday. A cooling trend will take place on Monday and Tuesday with temperatures lowering to near to slightly below normal by the middle of next week. && .DISCUSSION... Satellite imagery showing a surge of mid/upper moisture pushing northward through Kern and Tulare Counties. This moisture is producing some light rain showers and isolated thunderstorms mainly over the higher elevations of the Sierra Nevada as noted by radar composites (although KHNX is down at this time). With RH progs showing an increasing trend in moisture coming up from the south have increased POPs a bit for this afternoon and evening and also for later tonight and Friday as another surge is progged to move northward into our area toward daybreak. By Saturday the upper flow turns southwest which will push any tropcial moisture to the east of our area. The main concern for our area today; however, is temperatures which are currently running 6-10 Deg F higher than yday is the San Joaquin Valley, West Side Hills and Sierra foothills and 2-3 Deg F above yday in the Kern County Mountains and Deserts. An excessive Heat Warning remains in effect for these areas through Saturday evening as temperatures will remain near record territory over the higher elevations in Kern County on Friday and Saturday and will likely approach or exceed all time record highs in much of the San Joaquin Valley. Latest probabilistic guidance is indicating that Fresno has a 50 percent chance of exceeding it's record high on Friday of 107 Deg F and a 37 percent chance of exceeding it's record high on Saturday of 108 Deg F. Bakersfield has a 65 percent chance of exceeding it's record high on Friday of 106 Deg F and a 16 percent chance of exceeding it's record high on Saturday of 109 Deg F. Although the ridge remains inn place over our area on Sunday, an approaching upper low will produce increased onshore flow which will result in slightly cooler daytime temperatures although Sunday will still be much warmer than normal, and heat highlights might need to be considered by later shifts for Sunday across much of our area. The medium range models and their ensemble means are in fairly good agreement with lifting the low toward the Norcal coast on Monday then bringing it inland on Tuesday which will result in a baggy trough over central CA Tuesday through Thursday. Daytime temperatures will lower by several degrees on Monday and Tuesday with near to slightly below normal temepratures anticiapted for our area for Tuesday through Thursday with a dry southwest flow prevailing over our area for most of next week keeping our area under mainly clear skies. && .AVIATION... Areas of MVFR and local mountain obscuring IFR in low clouds, showers and thunderstorms over the Sierra Nevada and Tehachapi Mountains thru 03Z Fri and again after 09Z Fri. Otherwise, VFR conditions can be expected throughout the central CA interior for at least the next 24 hours. && .AIR QUALITY ISSUES... On Friday, June 18th, 2021, unhealthy for sensitive groups in Fresno, Kern, Kings, Madera, and Tulare Counties, as well as in Sequoia National Park and Forest. Further information is available at Valleyair.org. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low, medium, and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM PDT Saturday for CAZ179>191- 195>199. && public...DS aviation....Andersen weather.gov/hanford
The national radar mosaic for the moment the first event began.
2 thunderstorm wind. Local standard time, as filed.
California Highway Patrol reported wind gusts from a thunderstorm blew down a tree across Ave 400 3E Kingsburg blocking all lanes.
California Highway Patrol reported a tree was blown down during a thunderstorm near the intersection of SR 99 and Ming Ave in Bakersfield.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, June 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 955538, 955539.