  We obtain the superfluid weight and Berezinskii-Kosterlitz-Thouless (BKT)
transition temperature for highly unconventional superconducting states with
the coexistence of chiral d-wave superconductivity, charge density waves and
pair density waves in the strained graphene. Our results show that the
strain-induced flat bands can promote the superconducting transition
temperature approximately $50\%$ compared to that of the original doped
graphene, which suggests that the flat-band superconductivity is a potential
route to get superconductivity with higher critical temperatures. In
particular, we obtain the superfluid weight for the pure superconducting
pair-density-wave states from which the deduced superconducting transition
temperature is shown to be much lower than the gap-opening temperature of the
pair density wave, which is helpful to understand the phenomenon of the
pseudogap state in high-$T_c$ cuprate superconductors. Finally, we show that
the BKT transition temperature versus doping for strained graphene exhibits a
dome-like shape and it depends linearly on the spin-spin interaction strength.
