We have investigated the meterologically induced seasonal variation in the rotation rate of Mars. As on Earth, meteorological effects are expected to produce fluctuations in the rotation of Mars but unlike on Earth, where zonal winds are the major contributors, on Mars seasonal variations are mainly the result of exchange of CO2 between atmosphere and polar caps through a variation of the polar moment of inertia. From Viking pressure data and zonal winds models by Haberle et al. [1979> we predict an annual and a semi-annual cycles in the relative rotation rate of Mars of amplitude ~0.2¿10-8 and 0.1¿10-8 respectively. On the length of the martian day these seasonal changes are 0.17 ms and 0.09 ms respectively. Between the fail equinox and winter solstice (northern hemisphere), the maximum change in the martian l.o.d. amounts to 0.44 ms.