  We present temperature-dependent magneto-transport experiments around the
charge neutrality point in graphene and determine the amplitude of potential
fluctuations $s$ responsible for the formation of electron-hole puddles. The
experimental value $s \approx 20$ meV is considerably larger than in
conventional semiconductors which implies a strong localization of charge
carriers observable up to room temperature. Surprisingly, in the quantized
regime, the Hall resistivity overshoots the highest plateau values at high
temperatures. We demonstrate by model calculations that such a peculiar
behavior is expected in any system with coexisting electrons and holes when the
energy spectrum is quantized and the carriers are partially localized.
