Due to making Christmas week visits to the wife's relatives last night, I forgot to turn off the Christmas lights that I had wrapped around a 5-gallon containerized citrus tree of mine. The root zone temperature this morning was 142F (61C). The tree still looks fine, but it will now be the makings of an interesting experiment. I'll watch the tree over the next day or two to see what develops.

Millet
Niels Henrik David Bohr - Physicist (1885 - 1962)

Millet,
depending on my experience:

Trees respond with root damage to high root zone temperatures. But:
Time how long the temperature persist might here be the point, if the damage was found or not....

But, "boiling the roots" isn't realy fun, for me and many of my trees. As I found: Some plants do very well, but others do not tolerate such high temperatures....

It is now 5 days later, and the tree seems fine. I will have to be more careful in the future. - Millet