Once upon a time in America, men traded their felt winter hats for boaters on National Straw Hat Day every May and thus marked the unofficial start of summer. This year, in the coldest April in recent Tokyo history, the boaters are a season early, and it's the women who are wearing them.

While grown-up headwear, from square fedoras and berets to flowery katyusha hairbands and whimsical head-perching mini-hats, are all responsible for upgrading the era of hip-hop's baseball cap, it is the boater that is getting dressed up and down Tokyo. The Japanese name, kankan-bou (カンカン帽), like many fashion terms used in Japanese, comes from the hat's French name, the canotier.  A classic straw version with a simple, solid wide ribbon gets top billing on the pages of online hat retailer CA4LA.com, but simple is just the beginning.

In addition to the standard wheat straw and other natural materials such as sweet-smelling cypress and raffia, the hats come in a range of styles and fabric. Would you like that in linen, denim and cotton printed with tiny flowers? Even animal prints are prowling the spring streets. The band is endlessly customizable, showing up in sequins, nautical stripes and black and white polka dots. In step with the decofuku (decorated clothing), trend, people are adding bows,  flowers or bouquets of buttons.