I have 2 Cavaliers and I know they are susceptible to extreme temperatures.

I was posting to ask if it is safe to let them stay out in my backyard while I am at work. They seem to be happier when they are outside and I'd like to keep them out if possible. Obviously they would have as much water as they would need and a shaded area that they can go to.

Would this be safe or even with some shade/water would they still be in danger?