This August image from the fragmentary Walters Museum prayer book Walters W. 425 f. 8r features the astrological symbol for Virgo, the virgin, in the roundel on the top right, more flowers, and a very typical labor for August, threshing grain. The barn is open, allowing the chaff from the dried grain, which looks like wheat, to blow away, and to prevent the workers choking in the dust from the chaff. The flails look to the the sort where the actual flail is joined to the shaft of the handle with chain, allowing it to flex and thus be far more effective at removing the chaff without crushing the grain.
The weather is cooler, judging from their clothing, with layers, long sleeves, hats and stout shoes, appropriate for a task involving a flail. Based on the stack of sheaves behind the men, they have a lot of work ahead of them.