Were my actions really that irresponsible, all things considering?

All in all I don't think you were the least bit irresponsible. You happened to be a victim of cirstance (being the weather), and it's just unfortunate. You should try to explain to your parents about how you hadn't anticipated the fowl weather, and you reacted in a way that was quite responsible by making sure you were safe. You went to the support group because you needed to, and for them to think otherwise, especially when you lost a friend a little over a week before is downright insensitive and non-understanding. Realize that your parents are only angry because they were so worried (and rightfully so, if the weather was that bad and they received no information regarding your whereabouts or condition), but explain to them that you lacked the means to contact them (and that you had to go to the support group), and they need to be more trusting of your abilities. Relax and get some sleep (and even if your parents disagree, nobody here is really at fault), it'll cool down in time.