Third offense OWI carries significantly more severe penalties than first or second OWI. Unlike a second offense OWI in Wisconsin, there is no rule that your last offense had to occur within ten years. It includes any prior OWI convictions throughout your life.
The penalties of conviction include, but are not limited to, possible felony charges (particularly if a minor under 16 was a passenger at the time for your arrest), license revocation or suspension, a possible fine of up to $4,000, up to two years in jail, and permanent subjection to a PAC (prohibited alcohol concentration) of .02 in any state.
Several factors which may influence the specific penalties you face, including your specific blood alcohol content (BAC) and the presence of a minor passenger, among others.