Autumn kills more indoor cats than summer does, and almost never through cold. The 3 risk classes are poison, air and heat, and parasites, and they all peak in the same 8 to 10 weeks: rodenticide goes down before the first frost, windows shut and humidity drops, and fleas ride in on the last warm days. An 8 item check every 2 weeks, so 4 passes across the season, catches nearly all of it in under 25 minutes per pass.
Why every 2 weeks and not monthly
A cat's window for showing early weight loss is about 14 days: 50 to 80 g is measurable on a kitchen scale but invisible by eye, and at 4 weeks the same cat is 200 g down with muscle loss starting. Parasite cycles run on a similar clock, with flea eggs hatching in 2 to 12 days at 21 to 27 C. Poison exposure is the exception: it needs a check every 48 hours in the first week after bait goes out, which is why item 2 below is the 1 that does not wait for the 14 day pass.
The 3 risk classes and what autumn changes
Poison risk goes up because 3 products appear at once: anticoagulant bait stations in garages and neighbor gardens, ethylene glycol in winterised cars, and lawn treatments applied before dormancy. Air and heat risk goes up because the heating comes on, windows close, and relative humidity falls from 55 percent to 25 or 30 percent in 2 weeks, which dries the airway and the coat. Parasite risk goes up because fleas and ticks stay active until 4 to 6 C, and mice moving indoors carry fleas with them.
The 8 item table
Each pass takes 20 to 25 minutes, and the act column is the line where you move, not where you worry.
| Item | What you do | Act if | Risk class | Repeat |
|---|---|---|---|---|
| 1 Weight | Same scale, before breakfast | Change of 100 g or 3 percent | Metabolic | 14 days |
| 2 Bait audit | Walk 10 m around the house and garage | Any block within 5 m of the door | Poison | 48 hours |
| 3 Chemicals | Garage shelf, car top up bottles, lawn bags | Any open container below 1.2 m | Poison | 14 days |
| 4 Air | Hygrometer at cat height | Under 40 percent or over 65 percent | Air and heat | 14 days |
| 5 Heat sources | Hand test on radiators and heaters | Surface over 45 C, or cords within 30 cm | Air and heat | 14 days |
| 6 Coat and skin | Comb 3 areas for 2 minutes each | Flea dirt, scabs, or 1 bald patch over 2 cm | Parasite | 14 days |
| 7 Flea sample | White paper test on the cat's bed | 2 or more specks that turn red when wet | Parasite | 14 days |
| 8 Outdoors | Check balcony, doorstep and 3 plant pots | Mushrooms, snail bait, or 1 dead rodent | Poison | 14 days |
Log the 8 numbers after each pass; 4 dated lines per season make a trend a vet can act on.
Same checklist, 3 climate zones
The 8 items do not change with geography; the thresholds and the order do. In a cold continental zone with central heating, humidity is the item that fails first, often dropping to 22 to 28 percent by the second week of heating, so item 4 moves to the top and the target band is 40 to 55 percent. In a humid subtropical zone with no central heating, the indoor temperature can sit at 12 to 16 C with 75 to 85 percent humidity, so item 5 becomes about draughts and heated beds rather than radiator burns, and mold on window frames matters more than dry air. In a mild coastal zone, autumn is late and long, so the parasite items stay active into the 11th month and item 7 should run every 14 days until the first 3 consecutive nights below 6 C.
Two rules cross all 3 zones. Air the rooms for 10 minutes twice a day rather than cracking 1 window all evening, since a 10 minute exchange at 18 C costs less heat than 4 hours of a 3 cm gap.
Item 2 and 3: the poison pass
Anticoagulant rodenticide is the autumn killer, and the cat usually gets it second hand by eating a poisoned mouse, so a cat that brings in 1 rodent a week is at real risk. Walk a 10 m band around every door, check the 4 corners of the garage, and ask the 2 nearest neighbors whether they bait. If bait is within 5 m, assume exposure and call the vet with the product name and the estimated time, since signs can take 3 to 7 days to appear and wait-and-see is the wrong move. Ethylene glycol tastes sweet, and a spill of 5 ml on a garage floor is enough to matter: clean with paper towels, bag them, and keep the cat out for 24 hours. Full plant and product lists sit in the toxicity checker, and the season's mouse story is covered in the rodenticide guide.
Items 4 and 5: air, heat, and the 40 percent line
Dry air in a heated flat shows up as 3 things within 10 to 14 days: more static, a dull coat with 5 or more loose hairs per stroke, and sneezing 2 to 4 times a day. A 20 USD hygrometer at cat height settles the argument. Below 40 percent, add 1 wide water bowl per room, a humidifier set to 45 percent, and a 10 minute bathroom steam session twice a week if the cat tolerates it. Radiators above 45 C on the surface will burn a cat that sleeps against them for 6 hours; a 20 cm clearance or a folded blanket fixes it. Never leave a space heater on in a room the cat can enter alone, and keep cords 30 cm from any bed.
Items 6 to 8: parasites and the white paper test
Run a fine comb through the base of the tail, the neck, and the belly for 2 minutes each. Flea dirt looks like pepper and turns rust red on damp white paper, which is the cheapest test there is. Two specks is a finding. Autumn is also harvest mite season in dry grass, and those bites show as 5 to 10 orange scabs on the paws and ears, not as itching all over. Ringworm shows as 1 round patch with broken hairs at the edge, and it needs a vet, not a shampoo from a shelf. The weight item links to the season's scale routine in the autumn weight check.
5 steps for the first pass
- Weigh the cat tonight, before the evening meal, and write the number down.
- Walk the 10 m perimeter and photograph any bait station you find.
- Comb 3 areas and do the white paper test on the bed.
- Set a phone reminder for 14 days, then repeat the same 8 items 4 times this season.
Call the vet the same day for any of these: vomiting 3 or more times in 12 hours, blood in stool or urine, gums that look pale or white, a cat that stops eating for 24 hours, or 1 seizure. Those are not checklist items, they are the exit from the checklist.
Frequently asked
How often should an autumn cat check be done?
Every 2 weeks, so 4 passes across a 8 to 10 week autumn. Each pass covers 8 items and takes 20 to 25 minutes. The exception is the rodenticide audit, which runs every 48 hours for the first week after any bait is placed within 5 m of the house, because anticoagulant signs take 3 to 7 days to show.
What indoor humidity is safe for a cat in a heated flat?
40 to 55 percent at cat height. Central heating commonly pushes a room from 55 percent down to 25 or 30 percent within 2 weeks, which shows up as static, a dull coat and 2 to 4 sneezes a day. Below 40 percent, add water bowls, set a humidifier to 45 percent, and air rooms for 10 minutes twice a day.
My cat caught a mouse in the garden. Do I need the vet?
Call the vet and give the product name if you know bait was used nearby, since a cat that eats 1 poisoned rodent is the classic secondary exposure and signs can take 3 to 7 days. If you are certain no bait is within 5 m, monitor for 72 hours for vomiting, pale gums, weakness or bleeding, and go in at the first of those.