Moderator, Air Canada; FlyerTalk Evangelist
Join Date: Feb 2015
Location: YYC
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Posts: 18,984
If there's no availability showing now, best option is just to try to SDC when you land in IAH.
But I think you're being alarmist. The storms may not delay your arrival to IAH and you could still go sightseeing for a few hours. What were you planning on doing?
And if not, I'm pretty sure that with a 12-hour layover, you won't miss your connection, so worst-case scenario, you sit around the UA lounge for a few hours instead of seeing the city.