  We revisit the formation of a thermal population of hadronic axions in
nonstandard cosmologies, in light of the recent developments in obtaining
continuous and smooth interaction rates for both the gluon and photon
couplings. For certain cosmological histories, such as low-temperature
reheating (LTR) and kination-like scenarios, the thermalization of the axion
can be severely delayed to higher masses. In the case that thermal equilibrium
is achieved, we improve the constraints on LTR for axion masses around the eV
scale with respect to previous works and we constrain for the first time early
matter-dominated (EMD) cosmologies. We also point out the possibility of having
the co-existence of cold and warm dark matter populations of axions in
kination-like scenarios in the eV mass range.
