At What Point Do Cumulus Clouds Become Dangerous For Planes?

As a pilot, at what point do cumulus clouds start worrying you when you're out flying? This question was originally answered on Quora by Joe Shelton.

from Forbes Real Time http://www.forbes.com/sites/quora/2017/07/11/at-what-point-do-cumulus-clouds-become-dangerous-for-planes/
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