I had an interesting thing happen while gardening in my basement yesterday. I had mail ordered a baby saw palmetto palm tree and a crawling cactus called a crassula and I needed to mix up some potting soil for them to put them in bigger pots. Strangely enough, cactii and palms use the same mix of soil: Basically half peat/half sand with perlite to aerate it and some fertilizer. So I have this giant hay bale sized bag of peat I bought that will take the rest of my life to use up and unfortunately it has totally dried out into a big hardened boulder of brown dust. I have to break chunks of it off and strenuously squeeze and crumble it to mix it with the sand and stuff. But then when I would add water it wouldn't readily absorb the water and would float to the top of the flower pot and leave all the sand and the plant at the bottom.
So this time I decided to mix everything in a bucket of water to make sure it's all rehydrated before I put it in my pots. Stir, stir, squeeze, squeeze,.......hey......it's starting to get warm.......holy schit.......it's starting to get HOT. Steam was coming out of the bucket! Holy Bejeesus, was this happening when I potted my plants with dry peat and then watered them! The poor things were getting boiled by their new potting soil!
So I let the bucket sit for 1/2 an hour and looked up the phenomena on the Interweb. Yup, sure enough, peat gets hot and can even catch fire if the heat can't escape and the temps build and build. The glop in the bucket cooled off and I potted up my new plants.