We studied the impacts of climate variability on lowâelevation forests in the U.S. northern Rocky Mountains by quantifying how postâfire tree regeneration and radial growth varied with growingâseason climate. We reconstructed postâfire regeneration and radial growth rates of Pinus ponderosa and Pseudotsuga menziesii at 33 sites that burned between 1992 and 2007, by aging seedlings at the rootâshoot boundary. We also measured radial growth in adult trees from 12 additional sites that burned between 1900 and 1990. To quantify the relationship between climate and regeneration, we characterized seasonal climate before, during, and after recruitment pulses using superposed epoch analysis. To quantify growth sensitivity to climate, we performed moving regression analysis for each species and for juvenile and adult life stages. Climatic conditions favoring regeneration and tree growth differed between species. Water deficit and temperature were significantly lower than average during recruitment pulses of ponderosa pine, suggesting that germinationâyear climate limits regeneration. Growing degree days were significantly higher than average during years with Douglasâfir recruitment pulses, but water deficit was significantly lower one year following pulses, suggesting moisture sensitivity in twoâyearâold seedlings. Growth was also sensitive to water deficit, but effects varied between life stages, species, and through time, with juvenile ponderosa pine growth more sensitive to climate than adult growth and juvenile Douglasâfir growth. Increasing water deficit corresponded with reduced adult growth of both species. Increases in maximum temperature and water deficit corresponded with increases in juvenile growth of both species in the early 20th century but strong reductions in growth for juvenile ponderosa pine in recent decades. Changing sensitivity of growth to climate suggests that increased temperature and water deficit may be pushing these species toward the edge of their climatic tolerances. Our study demonstrates increased vulnerability of dry mixedâconifer forests to postâfire regeneration failures and decreased growth as temperatures and drought increase. Shifts toward unfavorable conditions for regeneration and juvenile growth may alter the composition and resilience of lowâelevation forests to future climate and fire activity.