I HIGHLY recommend wearing Under Armour Heat Gear shirt under the vest. Last summer I did an Iron Butt SaddleSoar 1000 ride as a fundraiser for Relay For Life - American Cancer Society. The date was fixed months in advance - the ride had to go on no matter the weather. The high during the afternoon was 95-100 deg F! The vest worked great. And, the Under Armour wicked any moisture away. I never felt "clammy" and the shirt was totally fine after the ride. Under Armour + Ride Cool = THE combination!!! We've ordered one for my wife -

Rating: [5 of 5 Stars!]