Glad you are tolerant of their presence and realize what a benefit they are to your environment. Bet it's a young one that decided to roost there rather than returning to it's regular roosting area. I'd just keep an eye one it and as long as it leaves tonight to feed, you probably won't see it again except on the wing. Then again, if you normally close the umbrella at night, it may have decided this is a pretty comfy pad. LOL.
If it doesn't leave, I would contact a wildlife rehabber. They will have more info for you and may want to come get it for observation. Contrary to the horror stories, most bats we see roosting near our homes are not rabid nor any danger to humans. Most people would be surprised at how many nocturnal critters live within our trees and yards and we never see them!

I'd have to say "Ditto" to Nancy's post in it's entirety! The only thing I'd add is that if you enjoy having the bat(s) around--you might try to put up a bat house to give them a place to roost that's more fitting than the umbrella. Bats are great--and if they "give" you guano--it's great fertilzer! :)

Here is a link that might be useful: Info on bats and bat houses

Count me with the other two for the most part:). It may be a male bat looking for a temporary roost. The females often kick the males out of the colony during pupping season and your season has probably just started. If the bat were sick, it would not move to a better place when you disturbed it. A note: animal rehab people don't generally take animals for "observation" they'd most likely tell you to leave it alone if it doesn't bother you having him live there for a while.

I second the bat house notion and recommend batcon.org for excellent information.

I'll ditto what everyone has said. I'd be so excited to find a bat in an umbrella, I'd probably move the umbrella somewhere close (but where guano wouldn't be a problem) and let the bat have it! :)

I was excited to find it and sorry my family wasn't around to see it.
It wasn't there this morning, so I suspect it was just temporary. I really don't think it would've stayed when it got hot any way. It has southern exposure and it was about 90 yesterday.
We have forested land around us, so they don't lack for roosting places. They come around the yard every evening and I sometimes will just sit and watch them. As a kid, friends and I would hit tennis balls into the air and watch the bats go after it. This was near a street light, so there were a lot of insects around.

My dad did the exact same thing! He about jumped out of his skin...lol. He took to leaving the umbrella opened, and the bat hasn't returned. I bought him a bat house years ago for father's day. He's never had a bat in it...lol...only the umbrella!

I'm happy to report that my dad finally installed both bat houses and he know has bats in both!