  We consider the non-analytic temperature dependences of the specific heat
coefficient, C(T)/T, and spin susceptibility, \chi_{s} (T), of 2D interacting
fermions beyond the weak-coupling limit. We demonstrate within the
Luttinger-Ward formalism that the leading temperature dependences of C(T)/T and
\chi_s (T) are linear in T, and are described by the Fermi liquid theory. We
show that these temperature dependences are universally determined by the
states near the Fermi level and, for a generic interaction, are expressed via
the spin and charge components of the exact backscattering amplitude of
quasi-particles. We compare our theory to recent experiments on monolayers of
3He.
