Yukata = Summer Kimono

For those wondering what a Yukata is, here is the answer from wikipedia.

A yukata (浴衣?) is a Japanese garment, a casual summer kimono usually made of cotton. People wearing yukata are a common sight in Japan at fireworks displays, bon-odori festivals, and other summer events. The yukata is also frequently worn after bathing at traditional Japanese inns. Though their use is not limited to after-bath wear, yukata literally means bath(ing) clothes.
Like other forms of traditional Japanese clothing, yukata are made with straight seams and wide sleeves. Unlike formal kimono, which are made of silk, yukata are typically made of cotton or synthetic fabrics, and are unlined.
Traditionally yukata were mostly made of indigo-dyed cotton but today a wide variety of colors and designs are available. As with kimono, the general rule with yukata is that younger people wear brighter colors and bolder patterns than older people. A child might wear a multicolored print and a young woman, a floral print, while an older woman would confine herself to a traditional dark blue with geometric patterns. Since the late 1990s, yukata have experienced a revival.

Customs:
Women in yukata, from behind to show the obi and fans, in Tokyo, Japan
The left side of the yukata is wrapped over the right side (commonly reversed with right over left when dressing a body for a funeral) and secured with an obi sash tied in a bow with the excess or with the koshi-himo and traditionally the bow is placed in the back. Traditionally bows in the front represented a prostitute. In private, such as after a bath, the yukata may be simply belted. Yukata are often worn with wooden sandals called geta, but tabi are not usually worn.

 

Resources:
https://en.wikipedia.org/wiki/Yukata
http://factsanddetails.com/japan/cat20/sub136/
http://web-japan.org/kidsweb/virtual/kimono/
http://web-japan.org/kidsweb/virtual/kimono/kimono01.html
http://www.japan-zone.com/culture/kimono.shtml