When I think summer, I think roses, lilac and lavender the most. To be honest my favorite scent in summer is basil and my fresh ripe tomatoes in the garden, but I don't know about washing with those scents!
You have to add cucumber and aloe to that list. That's pretty much a given for a summer scent. The coolness of cucumber is the epitome of summer to me. Watermelon is one of the scents I associate with summer too.
How would you feel about Honeysuckle or Jasmine? Scent is a very strong sense, and honestly, to me there is something so special about Honeysuckle. It reminds me of the freshness after a summer's rain. Not many things have Honeysuckle in them anymore. What a treat that would be!