Light = heat. Reduce the light and you reduce the heat.
Step 1: Before.
Step 2: How To.
Several rolls of oven rated aluminium foil
What to do:
Because of eaves on a building you will probably only need to cover the bottom half of the window. If there are no eaves then maybe the whole window (in two parts so the window can still be easily opened in case of emergency.)
Cut lengths of foil to cover the bottom half of the window. tape the foil to the window. Do that on just the top side only and let the foil hang down. Make sure that the shiny side is facing out to help reflect the heat. Window blinds should keep it in place. You want to make sure you can still get out easily in an emergency.
Once window is covered, go on to the next window if there is one.
Notice: Some home owners associations frown on such activity, You might also be associated with the tin foil hat crew. Showing off the reduced power bill will gain you followers.