Tropical Storm Hilary strengthened into a hurricane on Thursday morning and could become a major hurricane tonight or early Friday, the National Weather Service in Hanford said.

The current forecast calls for Hilary to weaken while moving north around the Baja Peninsula. But Hilary’s tropical moisture could bring excessive rain to Kern County’s mountains and desert, and the Sequoia National Forest on Sunday, the NWS said Thursday morning.

There’s also a 15% to 40% chance that heavy rainfall could extend to Fresno County and west across the San Joaquin Valley.

“Forecast rain amounts in the SJ Valley are from one-half to one inch with the higher amounts expected in the south Valley,” NWS said in its Thursday morning forecast discussion. “These rain amounts would bring the potential for flooding as well as rockslides and mudslides.”

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Meanwhile, Colin McCarthy, who tracks extreme weather throughout the world, tweeted that he’d “be storm chasing in Southern California Sunday/Monday, covering California’s first potential tropical cyclone landfall since 1939.”

Will be storm chasing in Southern California Sunday/Monday, covering California’s first potential tropical cyclone landfall since 1939.

Significant flash flooding will be the biggest threat, especially in southeast California deserts. pic.twitter.com/d33aTS8W68

— Colin McCarthy (@US_Stormwatch) August 17, 2023

Watch: Potential Hurricane Hilary Impacts on California  

Upcoming Forecast

It will continue to be sunny and hot Thursday with the high temperature topping out at about 104 degrees. However, Friday should bring an end to triple-digit temps with the high near 98. Similar conditions are expected Saturday.

The NWS says there’s a 20% chance of rain in the Fresno area before 11 a.m. on Sunday and a 40% chance after 11 p.m. The high temperature will dip to the low 90s.

Expect a 40% chance of rain on Monday and a 20% chance on Tuesday morning. The forecast calls for high temperatures in the 80s both days.