The mean large fire duration in the western US shows significant increasing trends of 0.76 days yr^-1 and 0.55 days yr^-1 for the summer and fall, respectively, during 1992-2020. Multiple linear regression models are used to examine the factors contributing to the trends and variability of large fire duration. Notably, the maximum daily wind speed during large fires, which has also increased during the study period, emerges as the primary predictor in both seasons. Comparison of the wind during large fires and on all days shows that the increasing maximum daily wind speed during large fires cannot be explained by the changes in the background wind, except for some small regions. Instead, the prolonged duration and increased extent of large fires may have contributed to the increase in maximum wind speed during fires by generating heat and smoke, and through the fire-wind feedback, we hypothesize that the wind changes may further prolong the fire duration and present challenges for fire control.