My daughter (3 yrs old) is refusing to go to playgroup next term. She's been really happy there, no tears, not even a 'I don't want to go..' until it thundered badly when they were playing outside once, followed by a downpour - first experience of this and 'on her own'. Now, she's scared of thunder and associates it with playgroup so no longer wants to go. Any tips on how to overcome this/ fun childrens books that might make light of thunder????