May is the month when flea eggs left by last autumn's survivors hatch in force and the first 30 C afternoon makes people switch the air conditioner on without thinking. Both jobs have a deadline you can measure: start flea control 4 to 6 weeks before the local peak, and test the AC on a mild 24 to 26 C day instead of the first hot one. Add a 24-hour water measurement and you have covered the three problems that are cheapest to fix in May and most expensive in July.
Why flea work starts 6 weeks early
Roughly 5 percent of a flea problem is on the cat. The other 95 percent is egg, larva and pupa in bedding, carpet and floor gaps. Eggs hatch in 2 to 14 days at 21 to 27 C, and larvae need 50 percent relative humidity; below 40 percent they dry out. In May, indoor humidity commonly sits at 55 to 70 percent and a floor strip by a sunny window reaches 24 to 28 C. That is why a cat clean in April is itchy by June.
The schedule is boring and cheap: treat every cat in the house on the same day, repeat at the label interval (commonly 4 weeks for spot-on, 8 to 12 weeks for an injectable or collar), vacuum floors and sofa seams daily for 7 to 10 days, and wash bedding at 60 C every 7 days for 3 weeks. A 5-minute flea comb over the rump and belly is the cheapest monitor you own: 1 flea in 7 days on a treated cat is a gap in the schedule, 3 or more means the room still produces adults. Pupae survive 6 to 12 months and survive most sprays, so vacuuming breaks the cycle, not the spray alone.
First air-conditioner run: 20 minutes, 3 checks
Run the unit for 20 to 30 minutes on a 24 to 26 C day before the cat needs it. Three things go wrong on first start: dust from 8 months of storage blows into the room, the drain pan has grown biofilm, and the thermostat overshoots. Clean or replace the filter before the test, check the drain outlet for standing water, and confirm the room holds within 1 to 2 C of the setpoint after 30 minutes. A unit that drops the room 6 to 8 C in 10 minutes on its first run is oversized for the space or set too low.
Set the target at 24 to 26 C, not 18 C; /seasonal/seasonal-heatwave-aircon/ covers multi-day runs. Cats thermoneutral zone sits near 20 to 28 C, and a 10 C swing between rooms pushes a cat to seek heat or hide. Keep the airflow off the resting spot: direct 1.5 to 2 m/s cold air on a sleeping cat at 22 C is a reliable way to trigger sneezing and eye discharge in a cat with herpesvirus. A cat that moves to the bathroom tiles for 2 days is telling you the setpoint is too low.
The 24-hour water log
Normal intake is 40 to 60 ml per kg per day, so a 4 kg cat drinks 160 to 240 ml, and a 5 kg cat 200 to 300 ml. Measure once, properly: fill a marked jug, put down only that water, and measure what is left after 24 hours; subtract spilled water if the bowl is tipped. Do it on 3 separate days in May because a single hot day reads 20 percent high. Dry-food cats land at the top of the range, wet-food cats near the bottom, and a cat eating 70 percent wet food may drink under 100 ml and still be fine.
Log the number next to the room temperature. A jump from 180 ml to 280 ml in 1 week with no heat wave is the earliest sign of diabetes mellitus or hyperthyroidism, both of which are treatable and both of which get harder after 6 months of drifting. A fall below 30 ml per kg for 2 days, or 0 ml in 12 hours, is a same-day call: cats concentrate urine well and can look normal at 10 percent dehydration.
May numbers at a glance
| Check | Target | Act when |
|---|---|---|
| Room temperature | 24-26 C | above 28 C for 3 hours |
| Water intake | 40-60 ml/kg/day | below 30 ml/kg for 2 days |
| Flea comb | 1 pass, 5 minutes daily | 3 fleas in 7 days |
| AC filter | clean every 14 days | visible dust at 10 days |
| Weight | within 5 percent of April | 200 g lost in 14 days |
| Bedding wash | 60 C every 7 days | itch persists 3 weeks |
When May turns into a vet visit
Book within 24 hours for any of these: resting breathing rate above 40 breaths per minute while asleep, open-mouth breathing, a water intake above 100 ml per kg per day for 3 days, vomiting 3 or more times in 24 hours, or a cat that stops grooming for 5 days. Flea allergy dermatitis — hair loss and crusts over the rump and tail base — needs a vet, not a stronger shampoo; the itch is an immune reaction to 1 flea bite and flea numbers can stay near zero while the skin stays red.
Heat stress is the other May trap. A cat in a closed room at 32 C with 60 percent humidity can reach a body temperature of 40 C in 40 minutes; signs are panting, drooling and wobbly walking. Cool with wet towels on the paws and belly, offer water, and drive to the clinic rather than waiting for it to pass. Do not put a cat in a cold bath: the peripheral vessels constrict and slow the cooling you are trying to achieve.
Cost of doing it now
A year of flea prevention for one 4 kg cat typically runs 60 to 180 USD depending on product class; treating a house infestation with professional pest control adds 150 to 400 USD and 8 to 12 weeks of daily vacuuming. The test costs 20 minutes and prevents an August compressor bill 5 to 10 times the price of a May service. Water logging costs 6 minutes a week and screens 2 endocrine diseases. Compare the recurring numbers in the /tools/cost/ calculator before choosing a product class, then run the flea timeline at /seasonal/seasonal-spring-flea-first-wave/ in the same week.
The May checklist
- Treat every cat on day 1, and write the next 3 dates in the calendar at 4-week intervals.
- Vacuum daily for 7 to 10 days, wash bedding at 60 C, and comb 5 minutes a day.
- Clean the AC filter, run 20 to 30 minutes at 24 to 26 C, and keep airflow off the bed.
- Measure water on 3 days and record it next to the room temperature.
- Weigh the cat on the same scale, at the same time of day, once a week.
If the flea count is still above 3 a week after 6 weeks of correct timing, the schedule is fine and the environment is not — switch to a product with a different adulticide class and keep vacuuming. If water intake doubles and stays there for 7 days, skip the second month of monitoring and book the blood panel.
Frequently asked
When exactly should flea prevention start in spring?
Start 4 to 6 weeks before your area's flea peak, which usually means late April to early May in a temperate climate. Eggs hatch in 2 to 14 days once floor temperature passes 21 C, and the pupal stage survives 6 to 12 months, so treating after you see fleas means fighting a reservoir that is already 3 to 4 weeks old.
Is 18 C too cold to set the air conditioner for a cat?
Yes for most homes. Set it to 24 to 26 C and keep airflow off the sleeping spot. A cat's comfortable range is roughly 20 to 28 C, and a 10 C difference between rooms makes it shuttle between heat sources. Direct cold air at 1.5 to 2 m/s on a sleeping cat can trigger sneezing and eye discharge.
How much water should a 4 kg cat drink in a day?
Between 160 and 240 ml from the bowl if it eats dry food, less if it eats wet food, since wet food is about 75 percent water. Measure once on 3 separate days in May. A rise above 100 ml per kg per day for 3 days, or a fall below 30 ml per kg for 2 days, needs a vet call.