EMB 170 Captain reported a severe turbulence encounter during cruise flight. Captain reported speed and altitude excursions and later climbed for a smoother ride.

Narrative

We were at cruise at FL330 in clear air above the clouds. Rides had been smooth up until this point; as well as on the flight along the same area on our way to ZZZ. While looking at the weather preflight we were aware of a pretty widespread system of scattered storms in the area; but knew the tops were around FL230-270. Both of our radars were on; in ACT mode; we were not picking up anything and ATC had not advised us of any weather along our route. Rides were smooth; and we could see out in front of us. All of a sudden we got a slight roll up and down; I immediately turned on the seatbelt sign and about 10 seconds later we encountered what I would characterize as severe turbulence. According the the FOM description; what fits the most is the large changes in airspeed. We had the aircraft under control but had large variations in speed and attitude. Upon reporting it to ATC we were told higher was better; so I made the decision to try to climb out of it once the worst was over instead of descending down into the clouds. Immediately after we were out of the severe w checked on the flight attendants and passengers. Everyone was okay and no structural damage was suspected. Upon landing I wrote it in the logbook and called maintenance. I told him I do not believe we exceeded any limitations; but a lot happened quick so It's possible we very briefly exceeded VMO and I didn't catch it; as I was focused on exiting the turbulence.