Updated March 13th: The USPS says these stamps will be issued October 4 in Brooklyn, NY.
From the USPS, November 22nd, 2016:
In 2017, Ezra Jack Keats’ most beloved story, “The Snowy Day,” will be showcased. Written and illustrated by the celebrated children author, it was one of the first prominent 20th-century picture books centered on an African-American child. Each of the four new stamps in this 20-stamp booklet features a different illustration of main character Peter exploring and playing in his neighborhood while wearing his iconic red snowsuit. The images include: Peter forming a snowball, Peter sliding down a mountain of snow, Peter making a snow angel, and Peter leaving footprints in the snow. Art director Antonio Alcalá designed the stamps with Ezra Jack Keat’s original art.