Q.Nurturing my tree until planting
I bought a weeping cherry at a garden center. Our local nursery advised to not plant til Sept.
QUESTION: How do I nurse it til then? It’s in the container on my patio in full sun and I am watering it daily.

The best time of year to plant your Weeping Cherry Tree is spring or fall. I would agree to hold off to plant until the weather at least begins to cool off.
We are in the hottest part of summer and it can be difficult to keep a stressed plant happy.
I would keep the potted tree in a partial sun location. Morning sun with shade from the afternoon sunshine. Water the tree daily and even twice a day if the soil is dry.
Here is a link that has information on planting and care.
https://www.gardeningknowhow.com/ornamental/trees/weeping-cherry/weeping-cherry-growing-tips.htm