Which is probably not all that often, given what we know about the Libyan climate:
"Less than 2 percent of the national territory receives enough rainfall for settled agriculture, the heaviest precipitation occurring in the Jabal al Akhdar zone of Cyrenaica, where annual rainfall of 400 to 600 millimeters is recorded. All other areas of the country receive less than 400 millimeters, and in the Sahara 50 millimeters or less occurs. Rainfall is often erratic, and a pronounced drought may extend over two seasons."
EVery time I consider using my feet as an umbrella, I run into the practical difficulty that they are, you know, under my body. This seems to place a severe limit on their potential use as an umbrella, regardless of their size.
Do these Sciapodes walk on their hands or something? Otherwise, I'm having a hard time understanding how this works.