I was trudging through an extremely hot Europe nearly two years ago, and most of my scents conked out. The only one that just kept going and going was Azzarro's Chrome, a citrusy lavender scent perfect for warm to hot weather. Unlike the others, it wouldn't wash away with perspiration.
Salvador Dali's Laguna was my second longest lasting.
Other good ones I like with good lasting power in less severe summer circumstances include Tommy T, Versace Green Jeans, Halston Unbound, L'Eau D'Issey, Kenzo Homme, Aqua di Portofino, Rochas Aquaman, Rochas Lui, Nautica Latitude Longitude, Michael Jordan Cologne.
Before buying any scent, spray some on the back of your hand and walk away. If it's still there with some strength after 3 hours, there's a good probability it'll last most of the day on you. If it's weak or totally gone by the three hour mark, don't bother with it - your skin and it are not meant for each other.