Newborn puppies can’t control their own body temperature for their first weeks, so breeders rightly focus on keeping them warm — but in a summer heat wave the danger can flip, and a whelping box with a heat lamp in a sunny room can overheat puppies and exhaust their mother.
The most important first
- Newborns can’t cool themselves. They depend on the room, the box and their mother.
- Measure, don’t guess. Put a thermometer at puppy level in the box; heat sources can run hotter than their setting.
- Give a temperature gradient: a warmer area and a cooler area, so puppies and dam can move.
- Watch the puppies. Quiet, feeding and gaining weight is good; restless, crying or crawling away from the heat means adjust.
- Look after the dam: fresh water at all times, a cool place to rest and close checks on her mammary glands.
Last updated: November 8, 2026
Why heat matters for newborns
Christensen and Erb (2024) note that neonatal puppies have a reduced capacity to regulate temperature and are vulnerable to both chilling and overheating. They describe how core temperatures below 35.0°C (95°F) lead to slow heart rate, breathing difficulty, loss of the suckle reflex, low blood sugar and organ failure, while temperatures above 41.1°C (106°F) can cause fluid in the lungs, bleeding and death.
The Royal Kennel Club advises keeping the whelping box at about 29–32°C (84–90°F) at first and lowering the temperature gradually each week until it reaches room temperature by week four. On a hot summer day, the room alone may already be in that range — and extra heat may not be needed at all.
Measure at puppy level
Don’t trust a thermostat setting. When Christensen and Erb tested five veterinary neonatal incubators set to 35°C, three ran more than 2°C hotter than their setting, and temperatures at times went above 41°C. A heat lamp or heat pad in a warm room can do the same.
Moxon and England (2012), writing on neonatal care, recommend placing a thermometer directly in the whelping box, and giving the dam and puppies access to a cooler area so the nest doesn’t overheat. They recommend infrared lamps over hot water bottles and heat pads, which carry a risk of burns.
Reading the puppies
The Royal Kennel Club explains that puppies at the right temperature are quiet, feeding and gaining weight. If they are restless and crying, adjust the temperature: move them closer to their mother and add warmth if they feel cold, and reduce the heat if they are trying to move away from it.
Moxon and England describe healthy newborns as having a rounded, full belly and warm, elastic skin, sucking enthusiastically every 2–3 hours in the first few days, gaining 5–10% of body weight a day and roughly doubling their birth weight by days 10–12. Daily weighing is one of the best early warnings that something — including the temperature — is wrong.
In practice
A breeder’s litter arrives during a July heat wave. She switches off the heat lamp after the first day because a thermometer at puppy level reads 31°C without it, closes the blinds, runs a fan in the room (not aimed at the box) and moves the dam’s water bowl beside the whelping box. When the puppies start sprawling apart in the afternoons, she drapes a damp sheet over one end of the box to make a cooler corner, and keeps weighing them twice a day.
(Illustrative, composite scenario.)
Practical steps for a summer litter
- Choose the room carefully: shaded, well ventilated, away from south- or west-facing windows.
- Control the room, not just the box: blinds, fans moving air around the room, or air conditioning.
- Turn heat sources down or off when the room is already warm, and check at puppy level several times a day.
- Create a gradient: keep any heat source to one side or the center of the box, as the Royal Kennel Club suggests, so puppies can crawl away from it.
- Never put puppies in direct sun.
- Plan for power cuts and heat waves: know how you’ll keep the room cool, and have a backup.
The dam in hot weather
Adult dogs can overheat simply from hot weather: Hall, Carter and O’Neill (2020) found that hot weather alone triggered 12.9% of heat-related illness events in UK dogs, and that brachycephalic (flat-faced) dogs had higher odds — so a flat-faced dam needs extra care in a heat wave. Offer fresh water beside the whelping box at all times, a cooler spot where she can rest away from the puppies, and short toilet trips at the coolest times of day. The Royal Kennel Club advises calling the vet straight away for a foul-smelling discharge, bleeding, or nipples that look swollen, hot or red.
Pereira and colleagues (2024), reviewing how to assess newborns, stress the importance of evaluating the litter and the mother together, monitoring constantly and getting veterinary help early when a newborn shows subtle signs of illness.
The European Food Safety Authority’s 2023 review of welfare in commercial dog and cat breeding included housing temperature among the factors it assessed — a reminder that temperature control is a core welfare responsibility, not a detail.
When to call your veterinarian
- A puppy that is weak, not sucking, crying constantly, or feels hot or cold to the touch.
- Puppies that lose weight or fail to gain for a day.
- A dam who is panting heavily at rest, restless, wobbly, trembling or not eating.
- A dam with a foul-smelling discharge, bleeding, or swollen, hot or red mammary glands.
- If in doubt, call — your vet would rather hear from you early.
Work on it
A few minutes here will teach you more than re-reading the article.
Ask yourself
- Do I have a thermometer at puppy level in the whelping box?
- Can my puppies move away from the heat?
- How would I keep the whelping room cool in a heat wave or a power cut?
Find out & check
- Check your heat lamp or pad against an independent thermometer before your next litter.
Do one thing
- Put a min-max thermometer in the whelping box and record the readings twice a day.
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Sources & further reading
- Christensen BW, Erb HN (2024) — An investigation of the discrepancy between set and actual temperature of neonatal incubators: concern for hypothermia and hyperthermia. Journal of the American Veterinary Medical Association 262:68–71. doi.org
- The Royal Kennel Club — Caring for newborn puppies. thekennelclub.org.uk
- Moxon R, England G (2012) — Care of the neonate (part one). Veterinary Nursing Journal 27:10–13. bvna.org.uk
- Pereira KHNP, Fuchs KDM, Mendonça JC, Xavier GM, Câmara DR, Cruz RKS, Lourenço MLG (2024) — Neonatal Clinical Assessment of the Puppy and Kitten: How to Identify Newborns at Risk? Animals 14:3417. doi.org
- European Food Safety Authority (2023) — Scientific and technical assistance on welfare aspects related to housing and health of cats and dogs in commercial breeding establishments. EFSA Journal 21:e08213. doi.org
- Hall EJ, Carter AJ, O’Neill DG (2020) — Dogs Don’t Die Just in Hot Cars — Exertional Heat-Related Illness (Heatstroke) Is a Greater Threat to UK Dogs. Animals 10:1324. doi.org
Where evidence is limited, recommendations rest on established practice and expert judgment, and may be updated as knowledge develops. This is general information and does not replace advice from your veterinarian.
Next steps
- Read next: Heatstroke in breeding dogs and puppies.
- Related: Parvovirus and your litter · Kennel parasite control for dams and litters.
- Return to the guide: Raising a healthy litter.