Save it for cooler weather. Several friends got WaveCel helmets this year and wear 'em even in Texas summer heat. But the helmets looked hot and felt heavy to me.
I got a POC Omne Air Spin. Best ventilated helmet I've worn -- the design really scoops air across my scalp, and I can feel it even through my hair, which is long and thick. Other folks with POCs say the same of their Octal and Ventral helmets. POCs have thicker EPS foam than most helmets and should offer good protection.
The POC Omne Air Spin is their lowest priced helmet, more of a commuter style helmet but with excellent ventilation. The Octal and Ventral are more roadie oriented. But I'm pretty satisfied with the Omne Air Spin, although I can see the overhanging brow at the top of my peripheral vision when I'm in the drops on my road bikes.