Authorities are warning of extreme health and wildfire risks across California this week, as the longest heat wave of the year is set to kick off Tuesday, bringing triple-digit temperatures, with little overnight cooling, to the vast majority of the state.

“This is really just a long-duration heat event that will provide little to no overnight [temperature] relief,” said Antoinette Serrato, a National Weather Service meteorologist in Hanford, Calif. The heat wave is expected to bring dangerous temperatures through the Fourth of July holiday and into early next week in many areas, particularly across Northern California, the Central Valley and southwestern deserts, she said.