EMB-145 Captain reported entering an area of severe turbulence resulting in course and altitude deviations. The Captain regained control of the aircraft when the turbulence stopped; and they continued safely to destination.

Narrative

We were in cruise flight at 13000 ft; operating a Flight from ZZZ to ZZZ1. There had been a lot of bad weather in the area all day. We passed through some clouds that appeared to have tops of about 15000 ft. The radar was not indicating anything but very light scattered precipitation. As we entered the clouds we encountered severe turbulence. The aircraft was thrown down about 400 feet instantly with about twenty degrees of bank to the left. Speed increased towards the red line; 320 knots; and I deployed the spoilers. As we tried to climb back to our assigned altitude of 13000 ft we were continually thrown back down in altitude. After about a minute; the turbulence subsided to light turbulence and we proceeded to climb back to our assigned altitude and on course. We reported the severe turbulence and the deviation to ATC and continued to our destination without further incident.Suggestion: Possibly request a deviation around clouds when widespread bad weather has been occurring in the area.