https://phys.org/news/2018-06-nasa-tropical-depression-bud-mainland.html

Infrared data from the Moderate Resolution Imaging Spectroradiometer or MODIS instrument showed coldest cloud top temperatures were in thunderstorms flaring east of Bud's center. Bud's center was still over the Eastern Pacific Ocean, off the coast of western Mexico, but thunderstorms and rainfall extended over land from Bud's northeastern quadrant. Thunderstorms in that quadrant showed temperatures as cold as minus 63 degrees Fahrenheit (minus 53 degrees Celsius). Storms with cloud top temperatures that cold have the capability to produce heavy rainfall.

At 11 a.m. EDT on June 15, the National Hurricane Center (NHC) noted that "Bud and its remnants are expected to produce heavy rainfall over the Mexican state of Sonora and the southwestern United States." The Government of Mexico has discontinued the Tropical Storm Watch from Altata to Huatabampito, and there are no coastal watches or warnings in effect.