I've been noticing people have been swapping people from one job to another, and I heard that would cause the people to lose happiness because switching jobs is undesirable.
also one of my biggest mistake is to not have any laborers, because it is only them who transfers goods from the location it was created to the storage, and vice versa. it is also the reason why you might not get a building started because no one is around to actually move the supplies to the building for the builders to build it. or no one is cutting trees down.
so instead of switching jobs, use them as laborers instead and get other tasks that you would normally wouldnt have the man power to do during those time of year. like cutting more lumber, clearing an area for future development, or just let them move supplies around.
as for what is season dependent, only farms it seems. hunters only hunt if there is wildlife in the area, and each hunter can only hunt so much each season. the only other job that is semi seasonal is woodcutters since firewood is used most in the winter time, and is used less during the other seasons when its warm (though its still needed in the warm seasons for cooking apparently) so you'll notice that they'll meet the quota during the summer, and become inactive (unless your limit is much higher) and then winter time, it'll deplete quite quickly.