"Afternoon thunderstorms" refers to the occurrence of thunderstorms, which are storms with lightning, thunder, and heavy rain, specifically during the afternoon hours. Full definition
Late afternoon thunderstorms predicted. (baliwaves.com)
When surface temperature and humidity reach a threshold, clouds form which reduce incoming energy from the sun reaching the surface, particularly in Earth's vast oceanic tropics (where a disproportionate portion of it enters the climate system), while daily afternoon thunderstorms remove enough heat from surface areas to bring surface temperatures back into line. (carlineconomics.com)
Summer in Arizona and throughout the Southwest is monsoon season, which means a daily pattern of afternoon thunderstorms, flash floods, dramatic dust clouds and spectacular displays of lightning over the desert. (climatecentral.org)