Bold plaids were considered especially fashionable in the late-1910s. This ad for Amory, Browne & co. fabrics ran in the April 1919 edition of The Delineator.
Keeping warm could be pricey in the the era before cheap, mass-produced fashion. The coats on this page of the Fall 1918 Sears catalog would range from $115-$200 if adjusted for inflation.