If there's a natural disaster cutting off electricity for days, trading bitcoin should be least of your worries really. Priorities man.
You wont really bother or to problem this thing first when theres an electricity outage for sure you would find to secure first your family,loved ones on how to live without electricity rather than minding on how you would able to trade with bitcoins. This is just really a non sense question after all because not only bitcoin trading would be affected but all the things which been powered by electricity would be gone too.Imagine a life without energy for sure you would struggle on daily living knowing that we are already living on this convenient world because of gadgets or things which uses electricity.If its gone then were fucked up.
maybe what op means is after the security of the family and love ones.maybe he want to purchase something and needed to do withdrawals,this may his concerns but for sure only one answer is applicable,its a big NO,YOU CANT MAKE TRANSACTION WHEN THERES NO POWER..because internet connection is the tools to make all of what you need,and internet is useless without power.