How Often Should I Water My Weeping Willow Tree To Keep The Leaves From Falling Off?

Weeping Willow trees offer many benefits to those who wish to plant them. These extremely large trees are known for their drooping branches that provide privacy, shade and wind protection. In addition to that, they are beautiful showpieces regardless of where they are sitting. However, these trees thrive on water. This is why you often find the weeping willow growing near bodies of water.
It is great to plant your weeping willow nearby to a water source, but it is not necessary for the tree to survive. Weeping willows can live well in other spaces as long as they are taken care of properly. The key is being able to water them and recognize if they have too much or too little water.
You will immediately know that your weeping willow has had either too much or too little water by looking at the leaves. If the leaves are droopy or are falling off them that is a sign that the tree has been watered improperly. If you have given the tree the right amount of water, the leaves will appear crisp and healthy when you look at them.
The good news is that it is very hard to overwater a weeping willow. These trees love water and you can give them a lot of it before it becomes a problem. When the tree is first planted you want to water it quite often. You may even water it daily, depending on your temperature and how dry it is. Over time you will wean the watering down slowly. Eventually you will get to the point where you only water the tree one to two times a week.
If you live in an area with an excessive heat or dry spells you may want to increase the water during this time. Pay attention to the leaves on the tree and take note if they need further watering.

It's very hot right now and I'm watering my lawn every other day. All of a sudden my willows leaves are turning yellow and falling off like it's winter. It's an older tree. Should I water it more or should I just chalk it up to the intense heat?  It has been over 100 degreese for a few weeks. I need help!!

If you are watering that often, you are going to kill the tree. In some plants, when you over water, the leaves do just what you explained. Back off of the watering for about a week.
There is a chance that you have an infestation of some kind too. Take a good look at the leaves that have fallen, and look over the bark on the tree as well. If this is the case, you may need to have the tree treated. Hope this helps, good luck.

How often do I have to water a small transplanted weeping willow tree,with about a 2 inch trunk

At least twice a week, depending on the size of tree will determine how much water it will take, bigger trees take more water.