Warmth Is the Main Risk for a Campbell's in a Power Cut
A Campbell's dwarf hamster in a long power cut is threatened most by falling temperature, not darkness. In a Campbell's, normal hamster lighting needs are minimal, but a small body in a cooling house loses heat quickly, especially during a deep daytime sleep when he is not generating warmth by moving.
Move the enclosure away from windows, exterior walls, and door draughts into the most insulated interior room, ideally the room the household is also heating and occupying. Raise the enclosure off a cold floor onto a table or a folded blanket, and drape a breathable blanket over part of the enclosure to hold warmth in while leaving ventilation uncovered on one side.
Deepen the Nest and Warm From Outside
For a Campbell's dwarf hamster, extra bedding is the safest heater you own. Add a generous amount of unscented paper bedding so he can build a deeper nest than usual, and include plain cardboard or a wooden hide he can pack bedding inside; a hamster who can burrow fully will regulate his own temperature remarkably well.
For added warmth, fill bottles with warm, not boiling, water, wrap them in a towel, and place them against the outside of the enclosure where he tends to sleep. He gets gentle radiant warmth through the wall and can move away from it, which a heat source inside the enclosure would not allow. Refresh the bottles as they cool, and never place a candle, portable burner, or any combustion heater beside the enclosure, because fumes that barely register to you are dangerous to a small animal's airways.
Water, Food, and the Filtration Question
A Campbell's dwarf hamster does not depend on powered filtration, but a power cut still affects his basics. Check the water bottle's ball tip with a fingertip each time you pass, because bottles can airlock or freeze at the tip in a cold room, and a hamster who cannot drink will stop eating soon after.
Keep feeding his usual seed mix at the usual times, and resist offering large amounts of fresh, watery food during the cut, which can chill and upset a small gut.
Watch Him at His Own Active Hours
In a Campbell's power cut, judge his condition at dusk and during the evening, when he would naturally be up, running, and feeding. A hamster who emerges, pouches food, and moves normally is coping; a hamster who stays out in the open feeling cold to the touch, moves slowly, breathes fast, or ignores food across a full active period needs warmth restored urgently and veterinary advice.
Keep handling short and purposeful while the power is out, because every trip out of the nest into cold room air costs him heat. If he feels cold, warm him gradually against your covered hands or beside the wrapped bottles rather than with direct heat, and contact a vet if he does not become responsive and active as he warms. Note the times of your checks on paper by the enclosure so the pattern is visible at a glance.
Splitting the Checks So None Are Missed Overnight
A long Campbell's power cut usually means checks through the night, when bottles cool and room temperature bottoms out, and that is exactly when a single tired owner misses a round. Agree in advance who refreshes the warm bottles, who tests the drinking tip, and who does the dusk activity check.
Writing those jobs down with times beside the enclosure works, and logging them works better when several people share a house. Assigning the bottle, warmth, and activity checks for your Campbell's through KinsLe Care Teams, with each completed check timestamped, means the overnight round is confirmed done rather than fondly believed done.