The best season for Joshua Tree is probably early spring and the autumn seasons. But, I have climbed there even in the middle of winter. I would stay away from J Tree in summer. Way too hot.
Thank you for the visit, Rob,
"After the first glass, you see things as you wish they were. After the second, you see things as they are not. Finally, you see things as they really are, which is the most horrible thing in the world."
--Oscar Wilde on Absinthe