Q.CAN CROWN OF THORNS TOLERATE AZ SUN IN SUMMER?
full sun 110 to 114 degrees
Certified GKH Gardening Expert
Tucson is in USDA hardiness plant zone 9, so you are on the edge of its hardiness for outdoors (10 and higher). It can take temperatures and heat above 90 degrees F, so you can make a judgement call here. Zone 9 still gets some below freezing temperatures and crown of thorns cannot tolerate frost. If it's in a container you can always bring it indoors for the winter. Here is more:
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/growing-crown-of-thorns-outdoors.htm
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm