March does 2 things at once: daylight passes 12 hours and the coat lets go, and the first warm week opens windows that have been shut since November. Both create measurable risk. A spring moult runs 2 to 4 weeks at 5 to 10 minutes of brushing a day, and a standard insect screen that has held for 4 months fails at 3 to 6 kg of push — about what a 4 kg cat generates landing on it from a sill. This month is an audit, room by room, window by window.
Why the coat lets go in week 2, not on 1 March
Shedding is driven by photoperiod, not temperature. Once daylight passes roughly 12 hours, the follicle cycle shifts and the undercoat releases over 14 to 28 days, with the peak usually 10 to 18 days after the switch. Indoor cats under artificial light can run 2 to 3 weeks early or late, which is why some flats are drowning in fur by 20 February and others in mid-April.
What comes off is the undercoat, not the guard hairs, and it comes off in tufts at the flanks and hindquarters first. A cat that is leaving 20 to 30 hairs on every hand stroke is in peak; one leaving 5 is at the start or the end.
Brush on a schedule, not on impulse
Shorthair: 5 to 10 minutes every other day, 10 to 15 minutes daily during the 2 to 3 peak weeks. Longhair: twice a day at peak, 5 to 8 minutes a session, plus a 2-minute check behind the ears and under the front legs where mats start. Undercoat rake 2 to 3 times a week; slicker brush the rest of the time; never a deshedding blade more than once a week, because it cuts guard hairs.
Bathing helps once, not weekly: 1 bath at peak removes more loose undercoat than 3 brushing sessions, then no bath for 6 to 8 weeks, since frequent washing strips the coat's oils and increases matting. Dry the cat fully — a damp undercoat at 18°C room temperature holds moisture against skin for hours.
Hairballs are the signal to watch. One every 4 to 6 weeks in a heavy-coated cat is common; more than 1 every 2 weeks, or any hairball with food in it, needs a vet visit, because the differential includes motility disease and obstruction, not just grooming.
Restart deworming on a 12-week clock
March is the natural restart because the first flea hatch and the first outdoor excursions line up. For a cat with garden or balcony access, most vets use a 12-week interval; for a confirmed hunter, monthly; for a fully indoor cat with no flea history, 1 to 2 treatments a year is often enough. Kittens run every 2 weeks to 12 weeks of age, then monthly to 6 months. Product choice and dose come from the vet — weight-based, and never from a human pharmacy.
Fleas follow the same calendar: monthly from March to November in most climates, year-round indoors with central heating. Treat every cat in the house on the same day; treating 1 of 2 cats leaves the population cycling in the untreated one, and a flea survives 1 to 2 weeks as an adult while pupae wait up to 6 months in carpet.
The window audit: 5 checks per opening
Do this in daylight, with the window open, on every opening in the flat. The failure mode is never the mesh itself — it is a 5 to 15 mm gap at the frame, a corner that has pulled out of its spline, or a screen held by 4 plastic clips that have gone brittle in 2 summers of UV.
| Location | Gap at frame | Load held 10 s | Verdict |
|---|---|---|---|
| Living room, south | 2 mm | 12 kg | Pass, recheck in 90 days |
| Bedroom, east | 8 mm | 3 kg | Fail, reseat spline today |
| Kitchen, sliding | 15 mm | 2 kg | Fail, add stopper at 5 cm |
| Bathroom, high | 1 mm | 15 kg | Pass, cat cannot reach |
| Balcony door | null, no screen | 0 kg | Fail, fit 5 cm mesh net |
| Hall, north | 4 mm | 8 kg | Marginal, tighten 4 clips |
Test with a 5 kg weight on a 10-second hang at the centre of the mesh and at each corner; anything that gives more than 10 mm fails. Then the gap test: a 6 mm Allen key should not pass between mesh and frame anywhere. Openings that slide need a stopper limiting travel to 5 cm, not a wedge the cat can knock out.
Balcony nets: the 3 numbers that matter
Mesh size 5 cm or less, breaking strength 15 kg or more, and 6 anchor points per 2 m of edge. A net fixed at 4 points with cable ties will hold a cat's weight once and then sag. Check the anchors every 90 days and after any storm, and replace the whole net every 3 to 5 years — UV degrades polypropylene faster than the label claims.
Where the winter weight goes
A cat that gained 200 to 400 g between November and February should lose it at 1 to 2 percent of body weight per month, no faster: 60 g a month on a 5 kg cat. Faster loss in a cat that is still eating is a vet flag. Shedding season is the easy window for this, because brushing 10 minutes a day burns more than the 5 minutes of winter grooming it replaces, and the coat change makes rib depth easier to feel.
5 steps for the first warm weekend
- Walk every window with a 6 mm key and a 5 kg weight; write the 2 numbers per window.
- Reseat or replace any screen with a gap over 6 mm and any screen under 10 kg.
- Fit stops so no opening passes 5 cm, and check the balcony net anchors at 6 points per 2 m.
- Book the deworming and write the next date 12 weeks out.
- Start daily brushing at 10 minutes and weigh the cat on the same scale as January.
Tools and coat-type routines are in spring shedding tools, the physics of falls and screen failure in window risk, and what prevention costs per month in the cost tool.
Terms mentioned in this article
Frequently asked
When does spring shedding start and how long does it last?
Once daylight passes about 12 hours, the undercoat releases over 14 to 28 days, with the peak 10 to 18 days after the switch. Indoor cats on artificial light can shift 2 to 3 weeks either way, so judge by the 20 to 30 hairs left on your hand per stroke, not by the calendar.
How often should an indoor cat be dewormed?
Most vets use a 12-week interval for cats with garden or balcony access, monthly for confirmed hunters, and 1 to 2 treatments a year for a fully indoor cat with no flea history. Kittens go every 2 weeks to 12 weeks of age, then monthly to 6 months, always dosed by weight.
How do I know if a window screen is cat-safe?
Hang 5 kg on the mesh centre and each corner for 10 seconds: more than 10 mm of give means it fails. Then check the gap — a 6 mm key must not pass between mesh and frame. Add a stop that limits the opening to 5 cm, and fix balcony nets at 6 points per 2 m.