A generally southerly hot wind originating in the Sahara that blows across Egypt from late March to early May.
[Arabic (rīḥ al-)ḫamsīn, (wind of the) 50 (days), khamsin, from oblique case of ḫamsūn, fifty, from ḫams, five; see ḫmš in the Appendix of Semitic roots.]
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