That week in May was my only "low" crowd trip. Honestly? I didn't notice a difference. Before deciding, I would check resort rates. If August is in value season, that's a bump for August. My May trip had shorter park hours. Maybe I didn't notice a difference in crowds because we all had to cram our parks into the same limited time frame? So, check historic park hours for most dates. I also didn't notice a difference in temperature. It was darn hot in May and August, but with a swim break from 1 or 2 until 5, it was fine.