Dear Tom,

Why do severe thunderstorms get weaker after the sun goes down?

—Benjamin Cohen

Dear Benjamin,

Severe thunderstorms frequently develop during the mid and late-afternoon hours on a hot and humid day. The sun’s heat causes surface air to rise, initiating the updraft process that triggers the thunderstorm development. Often, but not always, the thunderstorms begin to weaken as the sun sets, due to the loss of surface heating that diminishes the updraft process. However, there are also instances when t-storm activity increases at night. These nocturnal storms can also be severe and/or prolific precipitation producers. These thunderstorms develop at night with a warm, humid airmass in place at the surface and radiational cooling from the cloud tops increases instability initiating updrafts that trigger thunderstorm activity.