The IceCube Neutrino Observatory provides precise measurements of high-energy atmospheric leptons—muons and neutrinos—at unprecedented statistics. These leptons originate from cosmic-ray interactions in the atmosphere, predominantly via pion and kaon decays. Seasonal temperature variations in the stratosphere modulate the competition between meson decay and interaction, leading to measurable changes in the lepton flux. The effect becomes increasingly pronounced with energy. In this talk, I will discuss the evolution of IceCube’s measurements of seasonal variations, from early studies of overall rate modulations to recent analyses of their energy dependence, and show their impact on the characterization of the atmospheric neutrino flux.