With all this cheery weather in summertime...time for something nice!
Meaning
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A ray of sunshine is a good thing (of course). It can mean either one of two things:
1. A piece of positive news.
2. Someone who is a joy to be with.
Use in Normal Speech
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When getting good news.
"OK, so things didn't go according to plan in our operation, but hey, there is one ray of sunshine - we're learning all the time about how to make it work."
When describing someone.
"Leah's a real ray of sunshine, always positive and cheery."