January: Heating, Dry Air, and a Weight Baseline

January problems in a heated flat are measurable, not mysterious. Most forced-air rooms sit at 15 to 25 percent relative humidity while the thermostat holds 21 to 23°C, and a cat eating dry food needs about 45 to 60 ml of water per kg of body weight per day. Two checks in the first 7 days — a humidity reading at 1 m above the floor and a weigh-in to the nearest 10 g — catch most of what goes wrong before March.

Why dry heated air hits cats harder than people

Cats descend from desert hunters with a weak thirst drive: a cat that would drink 8 to 10 times a day from a stream drinks 3 or 4 times from a bowl. At 20 percent RH, respiratory water loss climbs by roughly 10 to 20 percent and the coat loses moisture faster than skin replaces it. Static builds on synthetic blankets and every touch is a small shock — which is why some cats quit the radiator-side perch in week 2 or 3 and move under the bed instead.

The signs arrive as a set, not one at a time: stool 1 grade firmer than usual, a coat that feels rougher at the tail base, 20 to 30 percent fewer urine clumps in the litter, and 5 to 10 extra nose licks an hour. Any one of those is noise. Three in the same week means the room is too dry.

Fix the room before you touch the bowl

Target 40 to 50 percent RH where the cat sleeps, measured at 1 m, with the room at 18 to 22°C. Under 30 percent, run a 2 to 4 litre evaporative humidifier and clean the tank every 3 days; an uncleaned tank grows biofilm in 48 to 72 hours and sprays it into the air the cat breathes. Over 60 percent you are growing mould instead, so air the room for 10 minutes twice a day.

Water: 2 or 3 bowls, each at least 12 cm across and filled to 3 cm, refreshed every 12 hours and kept 2 m from the food. Wide shallow bowls beat tall narrow ones because 30 to 40 percent of cats dislike whisker contact with the rim. A fountain lifts intake by 20 to 50 percent in some cats, and then the pump needs cleaning every 3 to 7 days.

Metric	Target	Check	If it is off
Relative humidity	40 to 50 percent	Daily, 1 m high	Add a 2 to 4 L humidifier below 30 percent
Room temperature	18 to 22°C	Daily	Move the bed 1 m off the radiator
Water intake	45 to 60 ml per kg per day	3 days a week by bowl level	Add stations; try a fountain
Body weight	Within 2 percent of baseline	Monthly, to 10 g	Vet visit at 5 percent over 3 months
Urine clumps	3 to 5 per day	Daily count	Vet if under 2 for 2 days
Vaccine due date	Every 1 to 3 years	Calendar	Book 2 weeks before it lapses

Build a weight baseline you can actually trust

Weigh monthly, same scale, same hour, before the first meal, and write the number down to 10 g. A healthy adult cat scores 5 of 9 on body condition: ribs felt under light pressure, a waist visible from above, a 1 to 2 cm abdominal fat pad. Track the trend, not the single reading. A 2 percent drop over 8 weeks or 5 percent over 3 months is a vet visit; 10 percent over 6 months is urgent.

Winter is when 200 to 400 g creeps on, because a cat that moves 20 percent less still asks for the same 60 to 70 kcal per kg. Cut the ration by 10 percent rather than switching food, and reweigh in 14 days. Two numbers 30 days apart beat one perfect memory.

Book the vaccine before the reminder expires

Core vaccines are FVRCP (herpesvirus, calicivirus, panleukopenia) and rabies. Adult boosters run every 1 to 3 years depending on the product and local law, and an indoor cat still needs rabies where the law demands it. FeLV deserves a conversation for any cat with balcony or garden access: 2 doses 3 to 4 weeks apart, then every 1 to 2 years.

January is the practical month for it. Most clinics run 30 to 40 percent quieter than in December, and a cat 2 or 3 weeks late carries less risk than one 2 months early. Ask for weight and temperature to be logged while you are there: 38.1 to 39.2°C is normal, and a January reading becomes the reference point for a July fever.

A 4-week plan for a 31-day month

1. Days 1 to 7: humidity logger in the sleeping room, 3 readings a day; first weight to 10 g; vaccine slot booked.
2. Days 8 to 14: humidifier cleaned and running; 3 water stations placed; count urine clumps for 24 hours.
3. Days 15 to 21: vaccine appointment; weigh again; watch the box for 48 hours, since roughly 1 in 10 cats avoids litter for a day after an injection.
4. Days 22 to 31: compare the 2 weights, trim the ration by 10 percent if the line is climbing, clean the humidifier tank for the 8th to 10th time.

When it stops being a comfort problem

Call a vet within 24 hours for any of 3 things: no urine for 24 hours (a blocked male can die in 48 to 72 hours), intake above 100 ml per kg per day for 3 days, or a 5 percent weight loss in 30 days. Those 3 numbers separate dry air from kidney disease, diabetes, and urethral obstruction.

5 steps for this week

• Buy a 10 to 20 currency-unit hygrometer and put it at 1 m in the sleeping room.
• Clean or replace the humidifier tank today, then every 3 days.
• Weigh the cat before the first meal and photograph the display.
• Move 1 water bowl into the room the cat spends the evening in.
• Check the vaccine card for a date older than 3 years.

None of this costs much: a hygrometer and 30 days of weighing cover the whole month, and the same 4 numbers — humidity, temperature, intake, weight — are what a vet will ask for first. For the heating-specific risks, see heating and dryness; the full cold-season list sits in the winter checklist, and monthly cost estimates are in the cost tool.

Terms mentioned in this article

FVRCP

Frequently asked

Related guides

• April Cat Checklist: Pollen, Ticks, 3 Garden Toxins
• August Cat Checklist: Humidity, Paw Pads, Travel
• December Cat Checklist: Plants, Food, Fireworks
• February Cat Checklist: Heat Cycle, Flea Eggs, Teeth
• July: Hot Pavement, Paw Burns, and Fountain Hygiene
• June: Heatwave Triggers, Wet Food, and Ear Checks