A single unusually cold night or a heating outage during a winter storm can undo months of good care in a matter of hours. Unlike the gradual seasonal slowdown covered in winter houseplant care, this is about the emergency response when indoor temperatures drop fast and unexpectedly — what to move, what to cover, and what to leave alone until things stabilize.

How cold is actually dangerous

Most common tropical and subtropical houseplants start showing cold stress once temperatures drop below about 50°F (10°C), with real damage becoming likely as things approach freezing. Not every plant is equally at risk — snake plant and ZZ plant tolerate a cold dip far better than delicate tropicals like calathea, alocasia, or a fiddle leaf fig, so if you have to prioritize, protect the most sensitive plants first and worry less about the tougher ones.

The biggest risk: window glass

A plant sitting against a cold window can experience temperatures much colder than the room itself, since glass conducts cold efficiently and offers almost no insulation. During a cold snap or outage, the single most useful thing you can do is move plants away from windows and exterior walls toward the interior of the home, even if that means a temporarily worse spot for light. A few days in mediocre light is a much smaller problem than a few hours pressed against freezing glass.

Group plants together

Clustering plants into one central, interior room does two things: it lets them buffer each other’s immediate surroundings a little, and it makes it far easier to cover or monitor everything as a group rather than checking on plants scattered through a cold house.

Insulate in place if you have to

If you can’t move a plant, or you’re dealing with an extended outage, loosely draping a sheet, towel, or even a cardboard box over it overnight can trap a bit of warmth, similar to how outdoor gardeners protect frost-sensitive plants. Avoid letting plastic touch the leaves directly if the plastic itself is cold — it can transfer cold straight to the leaf tissue instead of insulating it. Remove any covering once temperatures recover so the plant isn’t left in the dark longer than necessary.

If the power or heat is out for a while

Prioritize moving your most cold-sensitive plants to the warmest room you have, and consider consolidating everything into one space that’s easier to keep warm with a backup heat source if you have one. Be realistic: in a genuinely prolonged outage, some leaf damage on the most sensitive plants may be unavoidable. The goal in an emergency is keeping the plant alive, not keeping it undamaged — a plant that loses some leaves but survives can regrow; one left in the coldest spot in the house might not.

Ease off watering

Cut back on watering during a cold snap. Cold, wet soil is worse for roots than cold, dry soil, and a stressed, cold plant is taking up far less water than usual anyway. Watering on your normal schedule during a cold event just adds a second stressor on top of the temperature drop.

Assessing damage afterward

Cold-damaged leaves often turn dark, mushy, or black, sometimes appearing water-soaked before they collapse. Resist trimming anything right away — wait a few days to see the full extent of the damage, since tissue that looks bad immediately after a cold event can sometimes partially recover, and cutting too early risks removing more than necessary. Once it’s clear which parts are dead, trim them away and let the plant put its energy into new growth. Bring the plant back to its normal spot gradually rather than all at once, the same gradual-adjustment principle covered in how to acclimate a new houseplant, and resume normal watering and feeding only once you see it stabilizing.

After the emergency passes

Once temperatures and heating are back to normal, give plants a little time before resuming full care — a cold-stressed plant’s roots and leaves need to recover before they can make full use of water and light again. If a heating outage also left the air unusually dry, see how to increase humidity for houseplants to help sensitive plants recover a bit faster.