@Justin8
Unfortunately it's one of the T&Ca that you have agreed to. Adverse weather is one extenuating circumstance.
You can't force people to take out insurance - and even if they do, it will be much easier for them to claim from AirBnB than go through an insurance company. It's part and parcel of hosting.
Luckily (so far) in the UK (London) we don't have such adverse weather conditions, yet flights still get cancelled etc. and we just treat it as part of doing business. If it's one night and they arrive the following day, without asking we give them 50% (in cash) back from the unused night - pretty much guarantees you a 5* review.
I would try and turn this climate event into an advantage. Recognise that you are really trapped by AirBnB's policy - however, you can emphathise with the guest who was looking forward to their stay and tell them if they rebook you will give them a 10% discount. That would be my approach and I would be delighted if I was a guest and my holiday was ruined to get an email from a host with that offer... I'd rebook!
Keep safe!