When it's this cold out I don't think the old chuck the ice rule applies. I'm surprised there was even unfrozen sap in the pail.
I collected about 50 gallons from some buckets I put out last week to flush my RO didn't get around to flushing it out in time before it got cold and the sap is sitting frozen absolute solid in my Cage tank. Probley going to take a week for it to thaw out. Hopefully the tank and the valve survive. And of course i have it sitting in the most shady coolest spot on the property. So it never sees sun. Hard to believe we were getting thunderstorms last weekend at this time. -25 this weekend. Crazy weather.