how much heat does a ballast produce, a significant amount?
The hotter it is in the room/tent the hotter the ballast will be, always best to keep the ballast as cool as possible.
I live in OK too and the summer heat is what made me go LED. Can always supplement heat in the winter, but if you are going with anything else you will need supplemental AC in the summer and will make for a more expensive electric bill.
An old 600w magnetic ballast will add about 10% extra, a new one probably more like 5% or less.