On October 15, 2018, about 1310 eastern daylight time, Southwest Airlines flight 2437, a Boeing 737-7L9, N7816B, encountered turbulence while descending through about FL280. As a result of the turbulence, one flight attendant received serious injuries. The remaining passengers and crew were not injured, and the airplane was not damaged. The regularly scheduled passenger flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 from Chicago Midway International Airport (KMDW), Chicago, Illinois, to Manchester-Boston Regional Airport (KMHT), Manchester, New Hampshire. The flight crew stated that prior to encountering turbulence the seat belt sign had been illuminated, and the flight attendants had been asked to be seated since turbulence was anticipated. The flight crew stated that upon entering a “benign-looking” cloud formation the airplane encountered continuous moderate to heavy turbulence for about 20 to 30 seconds. The flight attendants (FA) stated that soon after receiving the call to be seated, the flight encountered turbulence and the FA in the aft galley was thrown against the door and cabinets, and then onto the floor, injuring her right foot. After landing the FA was transported to a local hospital and diagnosed with a broken right foot.