Rising temperatures on Wednesday posed new challenges for firefighters who have made incremental progress against a massive wildfire in central California that injured four people as it became the biggest blaze in the state so far this year.

The Gifford fire straddling a rural stretch of the Santa Barbara and San Luis Obispo county line continued to grow Monday, reaching 65,000 acres and 3% containment. Officials warn an upcoming heat wave will further challenge that firefight and bring widespread fire concerns.