Andres developed on May 8-9, 2021, marking the earliest formation of a tropical storm in the eastern Pacific Ocean since satellite records began in the early 1970s. The previous record was set by Tropical Storm Adrian on May 9-10, 2017. This is the third time in five years that a tropical storm has emerged in the eastern Pacific before the official start of the season on May 15. According to the U.S. National Hurricane Center, the average date for the first named storm in the eastern Pacific is June 10, with the first hurricane arriving by June 26. Due to prevailing westerly trade winds, most storms in the eastern Pacific move westward and rarely make landfall.