Trends of extreme precipitation (EP) using various combinations of average return intervals (ARIs) of 1, 2, 5, 10, and 20 years with durations of 1, 2, 5, 10, 20, and 30 days were calculated regionally across the contiguous U.S. Changes in the sign of the trend of EP vary by region as well as ARI and duration, despite the statistically significant upward trends for all combinations of EP thresholds when area-averaged across the contiguous U.S. Spatially, there is a pronounced east to west gradient in the trends of the EP with strong upward trends east of the Rocky Mountains. Generally, upward trends are larger and more significant for longer ARIs, but the contribution to the trend in total seasonal and annual precipitation is significantly larger for shorter ARIs as they occur more frequently. Across much of the contiguous U.S. upward trends of warm season EP are substantially larger compared to the cold season and have a substantially greater effect on the annual trend in total precipitation. This occurs even in areas where the total precipitation is nearly evenly divided between the cold and warm seasons. Compared to short-duration events long duration events, e.g. 30 days, contribute the most to annual trends. Coincident statistically significant upward trends of EP and precipitable water (PW) occur in many regions, especially during the warm season. Increases in PW are likely to be one of several factors responsible for the increase in EP (and average total precipitation) observed in many areas across the contiguous U.S.