Idiom: to burn off
Julie: Hey, do you want to go to the beach today?
Kathy: I don't know. It's really cloudy right now.
Julie: I know. California is like that in June. It's always cloudy in the morning but once the clouds burn off it'll be gorgeous.
Kathy: Really? Ok! Let's go then.
Tom: Did you guys go to the beach yesterday?
David: Yeah, we were going to go in the morning, but it was too cold and cloudy. We waited until the clouds burned off.
Tom: I bet the weather was amazing in the afternoon.
David: Yeah, it was perfect! Clear, sunny skies and not a lot of wind.
Meaning: "to burn off" is an idiom that is specifically used to talk about the process of morning clouds gradually disappearing. Usually along the coast in California the sky is cloudy in the morning. But then in the late morning or early afternoon the clouds go away and it becomes sunny and hot.