These are sudden gusts of wind. "It was the opinion," says Warburton, "of some philosophers that the vapors being congealed in the air by the cold, which is most intense in the morning, and being afterwards rarefied and let loose by the warmth of the sun, occasion those sudden and impetuous gusts of wind which were called flaws. Thus he comments on the following passage in Henry IV: "As humourous as winter, and as sudden as flaws congealed in the spring of day."--Rev. T. F. Thiselton-Dyer's Folk-lore of Shakespeare, 1884
A flaw of wind is a gust which is very violent upon a sudden, but quickly endeth.--Capt. John Smith's Sea Grammar, 1627
The falls of snow, which generally happen in March all over Great Britain, is in this neighbourhood called St. Causnan's Flaw.--Sir John Sinclair's Statistical Account of Scotland, 1791
November, the Windy Month,
was called wint-monath (literally "wind-month") by the Anglo-Saxons, a name foreshadowing the upcoming winter season.
Let the cheesy wind jokes beginneth.