Summer dream represents negative or dangerous situations that are happening over long periods of time. Not being able to think of anything except how “hot” a situation is. A prolonged time of risk or volatility. A boiling point type situation.
The symbolism is based on summer_time being the noticeably hottest and sweatiest time of year.
Alternatively, a summer or sunny day dream may reflect a good mood. Optimism you have about a situation.