Dog may just lay still or begin to twitch Dog's eyes may appear glassy. Temperatures can rise rapidly to 150 degrees even if the windows are left open.
Dogs can endure body temperature increases for only a short time or before suffering heatstroke.
Heatstroke can appear to develop quite suddenly. If your pet shows any of the signs of heatstroke, be prepared to take action immediately. Cool off the animal quickly. Soak it in cool, but not cold, water. In a severe case you may immerse the animal in a tub of cool water.