June or July

[MainMom]

If you plan on staying value or possibly moderate resorts I would choose June as this is where the tour groups stay in July.

 

[beccasmom]

July is hotter, but the crowds get smaller toward the end of the month, probably because some schools return in early August. I would chose June if lighter crowds were the objective, but it is still pretty warm and as schools close across the country, the crowds begin to increase. It's all relative.