How long can a dog last without water outside?

I left my dog at around 8 this morning with a full bowl of water and tied up in the covered patio. Its about 105 degrees outside and I won't be home till around 8:30 PST tonight and I'm worried she might be in trouble right now. I can't leave work and the neighbors are out on vacation. We have a pool but I don't think she can reach it since she's tied up. Our patio is pretty cool and has alot of shade but it still worries me. What should I do?