Pilot reported airspeed and altitude errors on approach to landing. After landing and taxi in; the pilot suspected a frozen Pitot Static System was the cause of the instrument errors.

Narrative

After the extensive and significant storms in recent days. I had pre-flighted the aircraft with the storms in mind. The aircraft is based on a flight line on an outside ramp. The flight was normal with all parameters normal up until the descent to landing. At that time; my airspeed indicator and my altimeter failed. While I managed to continue to fly without them; it took quite a few seconds to assess that there was a problem; and to determine a course of action. My airspeed indicator was indicating more than 30 knots high. My altimeter as I found out later was indicating about 250 feet high. Both of these situations are extremely unsafe; particularly when in the traffic pattern; and I discovered that I was low and slow and took a quick action to ameliorate the situation. I believe that the static system had water in it from the severe storms; and that it had frozen when I had gone up to altitude. It did not unfreeze until after I had brought the airplane to its parking spot and tied it down. Operationally; we are looking to modify our procedures; post storms; so that this does not happen again. An additional contributing factor is that my Passenger was feeling nauseous due to the local turbulence; which perhaps caused me a delay in recognizing that there was a problem. While I am happy that the flight resulted in a reasonable short final and landing; and I am grateful for my years experience; I believe that a more careful consideration of the effect of these historic storms on my aircraft would have served me well.