The way this year is going at least in Iowa Park (Texas), you need to keep your hand close to a water hose and use it to cool your plants and keep yourself hydrated. If you home your orchids outside, be sure they have a LOT of shade from 10:00 am to 5:00 pm every day. You probably should plan on watering them every day or at least spraying them heavily unless they are in really large pots. If you have mounted orchids, daily watering is a MUST unless you have a greenhouse.
If you have some cane type dendrobium phalaenopsis types which should be underpotted, they will LOVE water and light fertilizer as their new roots and growths are growing like gangbusters. These types of dendrobiums can grow three to four feet tall each year if they are standard ones. The leaves will bloom for several years. They will also keep their leaves for several years and the longsprays of white to purple flowers arch beautifully over the top of the foliage. These dendrobiums do not like to be re-potted. If you must do it, I would suggest waiting until new root tips can just be seen at the base of the new growth. Then I would only put the plant, pot and all, in the next pot size larger.
I repotted all of mine one time, all at the same time, and they ALL hated it. A number just died, and the others sulked for about 3 years before they started growing again. It was bad news all around. They are not growing like they should to this day about 6 years later.
Contributor: Bill Parker