While most people think that the northeast isn't all that hot; we have had quite a few days this summer. So I can confidently give you some suggestions, and perhaps you can compare them with others.
We stock Louis Garneau helmets in the shop, switched from Giro 7-8 years ago and have had GREAT results. With that said, the top two this season has been the Quartz(which is being worn in the pro ranks) and the Diamond. The Quartz sells for $140 with 23 vents,and the Diamond sells for $190 and has 47 vents. I own both of these, and can honesly say that they are very comfy and breath well.
Good luck in your search, and hopefully the weather cools down a bit for you!
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