No electrical power

2001 Sierra, when I turn to key over there’s absolutely no power, this morning I wiggled some alternator to battery wires and started right up. Went to the gas station and now won’t budge. I checked the terminals, they are tight. Could this be a wiring issue? It’s been hovering in the single digits temp wise for the last several days. Was running fine until it got this cold. Any advice is well appreciated.

Get a voltmeter to check battery voltage.(if not you're only guessing) Clean and tighten all battery cables.