Weather

Why California wildfires are so extreme right now

A rare mix of ingredients came together in central and northern California this week to produce fast-moving, explosively growing wildfires that are so powerful they create their own weather.

Noah Berger/AP

Lauren Tierney/The Washington Post. Source: NOAA Hazard Mapping System Fire and Smoke Product

The combination of an intense, long-lasting heat wave, dry vegetation at the end of the summer, and a rare outbreak of August thunderstorms led to these blazes.

Lauren Tierney/The Washington Post. Source: NOAA Hazard Mapping System Fire and Smoke Product

Aug. 18 | Napa, Calif.

Josh Edelson/AFP/Getty Images

Josh Edelson/AFP/Getty Images

Aug. 19 | Winters, Calif.

Noah Berger/AP

Noah Berger/AP

Driven by strong winds and aided by low humidity and high heat, the flames have kept firefighters on defense, at times resorting to helping residents evacuate rather than containing a blaze.

Complexes of multiple fires formed, prompting widespread evacuations on Aug. 18 and 19.

Noah Berger/AP

Aug. 18 | Carmel Valley, Calif.

Nic Coury/AP

Nic Coury/AP

Aug. 19 | Solano County, Calif.

Philip Pacheco/Bloomberg

Philip Pacheco/Bloomberg

The record heat reached astonishing levels during the past two weeks as a massive “heat dome” parked itself over the West.

Philip Pacheco/Bloomberg

On Aug. 16, Death Valley, Calif., reached 130 degrees, which if confirmed would be the highest temperature recorded during August and the third-hottest temperature on record for the entire planet.

Philip Pacheco/Bloomberg

Aug. 17 | Death Valley National Park

John Locher/AP

John Locher/AP

Aug. 18 | Death Valley National Park

Mario Tama/Getty Images

Mario Tama/Getty Images

Between Friday and Monday, the National Weather Service documented more than 140 record highs, including monthly records.

Oakland hit 100 degrees Saturday for the first time on record during August. Needles, in California’s southeastern desert, set an August record of 123 degrees on Saturday. And Sacramento set an August record of 112 degrees Sunday.

Mario Tama/Getty Images

Aug. 18 | San Francisco

Jeff Chiu/AP

Jeff Chiu/AP

Fueled by the heat, a round of thunderstorms on Sunday woke up residents of the Bay Area as a surge of tropical moisture pushed inland.

The storms’ lightning strikes sparked more than two dozen blazes, and erupted on multiple days. Dry thunderstorms, named because of their production of lightning without much rain, prowled inland areas, touching off new wildfires.

Jeff Chiu/AP

Aug. 16 | Oakland, Calif.

Noah Berger/AP

Noah Berger/AP

Aug. 16 | Healdsburg, Calif.

Kent Porter/AP

Kent Porter/AP

With climate change, wildfire season in California has been trending toward a year-long cycle rather than just lasting a few months as it once did.

What’s unusual about the ongoing event is the coincidence of a late-season, record-shattering heat wave with rare thunderstorms for this time of year. According to one estimate, California saw about 10 percent of its annual average lightning activity in just 3½ days.

Kent Porter/AP

Aug. 19 | California

CIRA/RAMMB

CIRA/RAMMB

August 18 | Napa County, Calif.

Noah Berger/AP

Noah Berger/AP

When conditions are extreme, with heat, dry conditions and bolt after bolt of lightning, you’re bound to see extreme fire behavior. However, the ongoing fires have spawned phenomena few have witnessed before.

Noah Berger/AP

Aug. 18 | Napa, Calif.

Justin Sullivan/Getty Images

Justin Sullivan/Getty Images

In Loyalton, Calif., a wildfire that raged Saturday released so much heat that its smoke plume grew sufficiently tall that it behaved like a thunderstorm. The smoky pyrocumulonimbus cloud tapped into changing winds with height, causing it to rotate and spawn several fire-induced tornadoes.

Justin Sullivan/Getty Images

Doppler radar revealed at least five tornado-strength rotational signatures inside the smoke plume, with photos taken from the ground of the smoky funnels

The National Weather Service in Reno, Nev., issued a souped-up tornado warning cautioning against the fire tornadoes and extreme fire behavior.

Justin Sullivan/Getty Images

Aug. 15 | Lassen County, Calif.

Katelynn & Jordan Hewlett/AP

Katelynn & Jordan Hewlett/AP

While this heat wave is beginning to wane, the Golden State is sure to see more blazes to come, until the wet season arrives in November or December.

Southern California for example, doesn’t tend to see its peak fire season until early fall.

Katelynn & Jordan Hewlett/AP

Aug. 19 | Sausalito, Calif.

Eric Risberg/AP

Eric Risberg/AP