As a rule of thumb, if the surface is too hot for you to walk on barefoot, it's too hot for your dog.
I have two black dogs. They got hot in direct sun. We avoid the hottest part of the day, we stick close to shade, and I bring water. Also, to keep their pads healthy I use musher's secret:
http://www.amazon.com/gp/aw/d/B0002...i=AC_SX236_SY340_QL65&keywords=mushers+secret
I have two black dogs. They got hot in direct sun. We avoid the hottest part of the day, we stick close to shade, and I bring water. Also, to keep their pads healthy I use musher's secret:
http://www.amazon.com/gp/aw/d/B0002...i=AC_SX236_SY340_QL65&keywords=mushers+secret