Abstract The effect of flowfield geometry on flame propagation and extinction of atmospheric CH4/N2/air flames was studied in the counterflow configuration. Laminar flame speeds and extinction strain rates for lean premixed and non-premixed flames were measured in axisymmetric burners producing either uniform or non-uniform axial velocity exit profiles. Particle image velocimetry was used to characterize the two-dimensional flowfield between the burners. The experiments were modeled with a one-dimensional code and a detailed C2 hydrocarbon kinetic model. Laminar flame speeds were found to be insensitive to the burner exit velocity profile shape but extinction measurements were strongly affected. In non-uniform flows, two-dimensional flow field measurements revealed significant radial dependence of flow quantities and high-speed video captured off-center initiation of extinction. Thus, centerline measurements did not represent the extinction state properly, given the direct contradiction to one-dimensional modeling assumptions, and the data was deemed unreliable for kinetic model validation. Flames in uniform flows were found to exhibit minimal radial dependence with extinction initiating at near-centerline locations.