I recently just returned from Singapore, where I spent a week trying to stay cool. The weather is hot year round and even at night. In fact people are often using umbrellas on hot sunny days to get a break from the beating sun. Not to mention rain tends to happen without notice and it isn't our wimpy California rain.
Considering that the umbrella is used as much for sun as for rain, why not put a fan in the umbrella to help with cooling off on hot days? That is what the Fanbrella does, it puts a fan inside of an umbrella. The Fanbrella runs off of six AA batteries and will run for about 5 1/2 hours. I like it.