"Unless they get their act together, which is unlikely, I have ordered FEMA to send no more money", the president declared.
"It is a disgraceful situation in lives & money!", the tweet says.
Trump deleted his tweet and reposted it to correct his spelling of the word "forest".
"He's already inviting illegal immigrants to his sanctuary state - everybody!" one said of Newsom.
This deserves a 5-star award for idiocy. And numerous state's worst fires don't happen in forests at all. No matter how many people with rakes they deploy, forests are going to burn b/c of longer, hotter summers due to climate chaos.More news: Fiji Water Girl steals the limelight at the Golden Globes
The Camp Fire in California past year was the costliest natural disaster anywhere in the world in 2018, with a total cost $16.5 billion, according to a report this week by the reinsurance company Munich RE.
California Democrats reacted angrily Wednesday to Trump's decision.
The California governor joined those of OR and Washington in asking the White House for more federal funding and assistance with forest management.More news: Alvaro Morata Edging Closer To LaLiga Return
FEMA is also impacted by the ongoing partial government shutdown and, as Washington Post reporter Damian Paletta highlighted, doesn't have money to send to the state.
Sen. Dianne Feinstein, D-California, called the tweet an "empty threat" and said it "isn't worth the time of day".
The 2018 wildfire season in California was the worst in living memory, consuming almost 2 million acres of land, killing 87 people, destroying tens of thousands of homes, requiring an estimated $3 billion in public expenditures for debris removal, and costing insurance companies over $9 billion in payments. The state's former top firefighter Ken Pimlott disagrees, saying last month that California leads the nation in clearing away dead trees and thinning areas to remove fuel for fires.
"We have been put in office by the voters to get things done, not to play games with lives", Newsom tweeted. "Attacking victims is yet another low for this president".More news: With Vic Fangio, Broncos go with experience and toughness