Assumptions:

• You are talking about a healthy human being
• Human being is not sitting in a car or truck or any other physical body
• Human being is oblivious to death by tree fall because he will not take any safety measures against it
• 'god_knows_when_probab' = a real number that belongs to [0 , 1]
• You will read this answer

% of area of space under a tree is 30% of the total area

Chances of rain to make the tree weak = 20% of the time (monsoon)

Odds of you being in that space = god_knows_when_probab

answer = 0.3*0.2*god_knows_when_probab.

I don't mean for this to be a troll answer. I am giving you a rough idea as to how you can arrive at the final answer. Thank you.

P.S: Yeah, they are all imaginary numbers, I have no references.