White walls are fine. Keep the air moving like everyone else said. Shut your lights off when your canopy reaches 105 (F). Drive your humidity down. From the heat your buds will be airier and you'll lose some weight. It's a trade off. I live and grow in the Mojave Desert. I do not air condition. I can't afford the electrical for that here and since I don't grow to sell (I breed and strain hunt for pain relief strains) I'm not willing to pay thousands more for electricity.
My canopy runs about 100 and I shut my lights off at 105. It doesn't hurt them. Running at night will help keep your temps lower (be scrupulous about light leaks). My humidity runs around 10% which helps. Still air will cook them so move air. Here is one of my girls at 10+ weeks today. The temp is about 90 in this pic and the odd light is the reflection from my Method 7's I put over the camera lens to filter out the HPS.
Best of luck with your grow.
View attachment 4613640