Mountaineering tents are heavy, strong tents built for high winds above tree line and unnecessary for regular backpacking. 4 season tents tend to be hot and humid in Spring through Fall because they are made to be closed up with full inner doors, flys that come down to the ground, and netting instead of mesh inner bodies to seal out the wind and wind blown snow. You can certainly get by with a 4 season or a 3+ season tent in the summer. I did for many years. However, buying two tents, which your budget allows as long as you stay away from Hilleberg and other very expensive tents, lets you get a very light 3 season tent with ventalation to help you stay comfortable on hot, humid nights and a heavier and tighter sealed tent for cold winter winds.