1999 Jeep Wrangler smoke pouring from the vents

A few months ago, white smoke started pouring from my vents. The water temp gauge redlined and I pulled over, waited for it to cool, added coolant and it has been fine. Last night, smoke started pouring from the vents again, but the temp gauge hasn't moved from it's usual position at right around 210. This morning I added coolant, but smoke is still pouring from the vents, a lot. There is a burning smell too, but no sign of fire or change in engine performance.