Not sure if anyone has suggested this, but what about sunstroke? It could be an environmental threat, alleviated by spending time in shade from structures or palm trees, thus adding more reason to grow them.
The difficulty with that, as well as the need for warmth in a day/night situation, would be balancing the early game when you're scrambling for resources to feed yourself, stay hydrated, and have a big enough raft to put other features on. It's pretty easy to die during that period as it is.