I have a pool the same size as yours and vacuuming 3-4 times a week is normal maintenance. I grew up with a 20 x 40 pool and we vacuumed every day. It's nice that you haven't needed to do that until now, but 2-3 times a week is pretty good IMO and anything less than that is unrealistic.
I'm assuming that you already brought a sample to the pool store and that your chlorine, stabilizer, Ph and alkalinity are fine. If the chlorine level is running low every couple of days and the chlorinator is working fine, then you have a vicious circle going where the algae are using up all of your chlorine and then there's no more chlorine so they grow. There is an algae called mustard algae that needs a different kind of algaecide to treat. I find that if the algae gets out of control, doing a yellow treat for mustard algae generally knocks things back a bit. And yes, the excessive heat and lack of rain can definitely be contributing factors.
If the algae is kid of dusty looking at the bottom of the pool and scatters when you put the vacuum near it, it may be the mustard algae. It's allegedly rare but we treat for it anyway and the treatment works.