First move: keep the warmth already inside the enclosure
A milk snake in a power cut is losing heat slowly, not all at once, and your first job is to slow that loss down. Leave the lid closed, because every opening dumps the warm air the enclosure still holds and invites a stressed snake to push toward the gap. Drape blankets, towels, or a spare duvet over the top and sides of the tank, leaving the covering loose enough that nothing presses on the lid. If the room itself is cold, move the whole enclosure into the smallest, warmest room you have, ideally one that gets body heat from the family gathering there. A milk snake kept at normal room temperature for some hours is uncomfortable, not in crisis, so resist dramatic fixes in the first hour.
Gentle warmth you can add without electricity
Added heat helps a milk snake only when it stays mild and stays outside the glass. Fill a bottle or sealable container with warm tap water, wrap it in a towel, and rest it against the outside of the warm end so a soft gradient forms through the glass. Hand warmers belong outside the enclosure too, taped to the outer wall under the blanket layer, never loose inside where a milk snake could lie directly against one and burn. As each bottle cools, swap it for a freshly warmed one rather than reheating aggressively. If you have a gas hob, warming replacement water is easy; if not, the blanket insulation alone carries a healthy milk snake through most outages.
What to leave undone until the power returns
Feeding waits until the heat has been back for a good while, because a milk snake cannot digest properly in a cold enclosure and a meal offered now risks regurgitation later. Handling waits too: a cool milk snake is stressed, more defensive than usual, and gains nothing from being carried around, however warm your hands feel. Skip candles and any open flame near the tank, and never pour hot water into the water bowl to steam the enclosure, since that swings temperature and humidity sharply in a small space. Also leave the substrate and hides exactly as they are; a milk snake wedged under its hide in the dark is doing precisely what it should, conserving energy and staying calm.
Watching your milk snake through the outage
Check the enclosure thermometer through the glass at intervals rather than lifting the lid to test the air with your hand. A milk snake that stays coiled in its hide, tongue-flicking occasionally when the blanket shifts, is coping normally. Worry signs are different: repeated gaping, wheezing or clicking sounds, mucus around the mouth, or a snake that lies limp and unresponsive when the enclosure is gently moved. Those signs during or after a long cold outage warrant a call to a reptile vet once travel is safe, especially if the snake recently ate or was already off its food. When the power returns, let the heat mat warm the enclosure gradually and confirm the thermostat is cycling before you treat the routine as normal again.
Splitting the outage checks fairly
One person refilling warm bottles at midnight while everyone else sleeps is how details get missed, so divide the watch into named jobs: thermometer checks, bottle swaps, and a final once-over when the lights come back. Writing those jobs down, with times, stops two people repeating one check while another never happens. KinsLe's Care Teams fits this exact scramble, letting you assign each outage task for your milk snake to a household member and see it marked complete with a timestamp, so the next person waking up knows the state of the tank at a glance.