Could be fungus gnats, they are often drawn to over watered trees, if the soil isn't drying down you speed up the composting of the organics in your soil.
If so I am guessing you water on a schedule(i.e. every morning) it's not always easy but try to only water when the tree needs it.
The heat index is 104 on average lately so I dont think its a good idea to put it outside.
What kind of tree is it and where do you live, important info to help you out.
The heat index thing isn't a big deal if other plants live outside, depending on species it's probably best to be outside, and air circulation is important, it also helps dry dpwn the soil.
Speaking of soil, whats in you pot, this could be the biggest part of the problem.