I won't take my dogs out until late evening in the summer.
I work in the foothills of Colorado, I have seen young labs come in dead from heatstroke in 90-95 degree weather after going on long hikes. No way would I risk it with a breed that has a thick double coat.
Plenty of water and rest, sticking to shade as much as possible is the best advice I can give other then don't do it. It's irresponsible, IMHO
~Emergency Vet Tech
Berlin vom Spartanville 1/13/13
5/25/07 - 2/9/15
2008 - 7/23/12
"Make sure my shepherd dog remains a working dog, for I have struggled all my life long for that aim." - Max Von Stephanitz