Hot Day on the Trail_IMG_0432-HDR, a photo by yukonchris on Flickr.
HDRs require that you merge multiple exposures covering several f-stops in order to get the dynamic range that a single shot just can't record. This photo is an example of how that process can result in an image that really feels as if it is approaching the reality you saw when you set up for the shots.
While I always recommend hiking as lightly as possible, especially on a very hot day, adding a few pounds of photographic gear isn't always a bad idea. Besides, it all serves to help keep one fit.