Water is the cheapest, simplest and most overlooked part of looking after a dog in hot weather. Most dogs drink what they need if water is always within reach, but heat changes the equation: dogs lose water by panting, they exercise in conditions that make them thirstier and a dog away from home may not find a drink. This guide gives you a plan: how much a dog normally drinks, how to carry and offer water, how to measure intake and which signs mean a vet is needed straight away. It is practical information, not a treatment guide; heat illness is an emergency for a vet.
The reference to start from
The Merck Veterinary Manual gives maintenance water for dogs of about 50 mL per kg of body weight a day, with a range of 40 to 60, and describes intake above 100 mL per kg a day as excessive (polydipsia). The Dog Water Intake Calculator uses these figures.
| Dog | Typical (50 mL/kg) | Range (40 to 60) | Call-the-vet line (100 mL/kg) |
|---|---|---|---|
| 5 kg | 250 mL | 200 to 300 mL | 500 mL |
| 10 kg | 500 mL | 400 to 600 mL | 1,000 mL |
| 20 kg | 1,000 mL | 800 to 1,200 mL | 2,000 mL |
| 30 kg | 1,500 mL | 1,200 to 1,800 mL | 3,000 mL |
| 40 kg | 2,000 mL | 1,600 to 2,400 mL | 4,000 mL |
These are guides for an ordinary day. Heat, exercise and a dry diet raise intake, and wet food lowers the bowl intake. In hot weather a dog may reasonably drink more than the typical figure; what matters is that it can drink as it needs, and that you notice big or sudden changes. Our guide to how much water a dog should drink covers the basics.
Water at home
- Several bowls. Put water in more than one place, in the shade and indoors, so that the dog never has to search.
- Stable bowls. A heavy ceramic or stainless-steel bowl is harder to tip.
- Fresh and cool. Refill often, because water warms and collects dirt in hot weather. Wash the bowls daily.
- Never restrict water. Offer small amounts more often if a dog gulps and vomits, but do not take the bowl away.
- Cooling spots. Provide shade and a cool floor for resting.
- Count the food. A dog on wet or mixed food gets some water from meals; see whether wet food counts toward water intake.
Water on walks and outings
Plan for the walk you are on, not the walk you hope for. A short stroll and a long hike need different amounts. A planning method: decide how long you will be out, offer a drink at the start, at intervals and at the end, and carry enough that you can keep doing so.
| Outing | Suggested planning |
|---|---|
| A short local walk | A small bottle and a collapsible bowl |
| A long walk or a day out | A larger bottle or two, and a way to refill |
| A hot day | Avoid the hottest part of the day, shorten the outing and carry extra |
| A car journey | Water and a bowl in the car, and regular stops |
Offer small drinks often rather than a large drink after hard exercise, which some dogs gulp and bring up. Do not let a dog drink from stagnant puddles or ponds; water in ponds and the sea can carry hazards, and you may not know what is in it. If you are unsure, carry your own.
The Pet Travel Food Calculator is for food, but the same planning applies to water on a long trip: work out the total for the days and dogs, and add a margin. If you track temperatures, the Pet Temperature Converter switches between Celsius and Fahrenheit.
Never leave a dog in a parked car
Temperatures inside a parked car can rise very quickly, even on a mild day and even with windows slightly open. Water in the car does not make it safe. If you are travelling with a dog, plan your stops so that someone can stay with the dog, or leave the dog at home. If you see a dog in distress in a parked car, follow local advice for contacting the authorities.
Measuring intake
If you want to know how much your dog drinks, measure for three ordinary days:
- Fill the bowl with a measured amount in the morning, and top up with measured amounts.
- At the end of the day, measure what remains and subtract. Allow for spills.
- Add the water from any wet food.
- Divide by the dog’s weight in kg.
For example, a 20 kg dog drinks 1,400 mL from the bowl on a hot day: 70 mL per kg, above the typical figure but below 100. Check against your dog’s normal. If it is drinking much more than usual without a change in heat or exercise, or more than 100 mL per kg for several days, call your vet. Take your measurements.
Signs of overheating
Overheating can become life-threatening quickly. Treat the following as an emergency and contact a vet immediately:
- Very heavy, noisy or rapid panting that does not settle with rest.
- Heavy drooling.
- Weakness, wobbliness, collapse or confusion.
- Vomiting or diarrhoea.
- Very red or very pale gums.
- A dog that will not move.
While you arrange help, move the dog to shade, and follow your vet’s advice on cooling. Do not wait to see whether it passes. Some dogs are at higher risk, including puppies, seniors, overweight dogs, thick-coated dogs and flat-faced breeds, and need extra care in hot weather.
Reducing the load on the dog
Hydration is only one part of coping with heat. Exercise early or late in the day, and avoid hot pavement. Shorten outings, and rest in shade. Keep a healthy weight, since extra weight makes heat harder to bear; our guide on whether a dog is overweight can help you check. Brush out loose undercoat, but ask a groomer or vet before clipping a double coat. Provide airflow or cooling in the home, and give extra attention to older and vulnerable dogs.
When a dog drinks less than usual
A dog that drinks much less than usual in hot weather, is lethargic, has dry or sticky gums, or refuses food needs a vet. Dehydration can build up silently. Do not force water, but offer it often, and call your vet for advice.
When a dog drinks much more than usual
Heat explains many cases of increased drinking, but a lasting or sudden large increase should be checked. Our guide on why a dog may be drinking so much water explains how a vet approaches it. Bring your measurements, a note of the weather and activity and a list of any medicines.
A checklist for a hot day
- Fresh water in two or more places, in the shade.
- Walks in the cool part of the day.
- A bottle and bowl for outings, plus extra.
- Never leave the dog in a parked car.
- Know the signs of overheating and your vet’s emergency number.
- Watch older, young, overweight and flat-faced dogs closely.
- Measure intake if you are worried.
Working out a trip’s water in advance
Planning prevents running short. Take the reference of 50 mL per kg a day, add a margin for heat and exercise, and multiply by the number of dogs and the hours out.
| Dog | Reference for a full day | Plus 50% for heat and exercise | For a 4-hour outing (one sixth of the day, with the margin) |
|---|---|---|---|
| 5 kg | 250 mL | 375 mL | 63 mL |
| 10 kg | 500 mL | 750 mL | 125 mL |
| 20 kg | 1,000 mL | 1,500 mL | 250 mL |
| 40 kg | 2,000 mL | 3,000 mL | 500 mL |
The figures are for planning only, and a hot day can raise a dog’s needs well above them. They show that the amounts are modest, which makes it easy to carry more than you think you need: a 40 kg dog on a hot four-hour outing might drink half a litre, and a litre is a sensible amount to carry. Round up, and take a way to refill.
Special cases
Puppies, seniors, pregnant or nursing dogs, dogs with health conditions and dogs on medication may have different needs. If your dog is on a medicine, ask your vet whether it affects thirst or heat tolerance. If your dog has a condition that affects drinking, follow your vet’s plan, and ask what to do in hot weather. Working dogs, such as those that run for long periods, need a plan agreed with their vet and handler.
Quick summary
- A dog’s water reference is about 50 mL per kg a day; above 100 mL per kg a day is a reason to call your vet.
- Offer fresh water often at home and on outings, and never restrict it.
- Carry more than you think you need, and offer small drinks regularly.
- Never leave a dog in a parked car.
- Collapse, heavy drooling, vomiting or heavy panting that does not settle are emergencies.
- Use the Dog Water Intake Calculator.
Frequently asked questions
How much water does a dog need in hot weather?
The reference is about 50 mL per kg a day (40 to 60). Heat and exercise raise intake, so offer water often and let the dog drink to its needs. Drinking above 100 mL per kg a day, or suddenly more, is a reason to call your vet.
How much water should I carry on a walk?
Enough to offer small drinks regularly. As a planning figure, carry at least a few hundred millilitres for a small dog and more for a large one, and take extra on long or hot outings.
Should I limit a dog's water in hot weather?
No. Do not restrict water. Offer small amounts often if the dog gulps.
What are the signs of overheating?
Very heavy or noisy panting, heavy drooling, weakness, vomiting, wobbliness or collapse. Treat these as an emergency and call a vet immediately.
Can I leave my dog in a parked car if I leave water?
No. Never leave a dog in a parked car, even briefly, even with water.
Does wet food help in hot weather?
It adds water to the diet, but fresh drinking water must still be available all day.
Sources
- Merck Veterinary Manual — maintenance water about 50 mL/kg/day (range 40 to 60); more than 100 mL/kg/day is polydipsia
- NRC (2006) Nutrient Requirements of Dogs and Cats, National Academies Press
Related calculators
- Dog Water Intake CalculatorEstimate how much water your dog should drink in a day and check whether the amount it drinks is normal.
- Pet Travel Food CalculatorWork out how much pet food to pack for a trip, with spare days.
- Pet Temperature ConverterConvert aquarium, room and water temperatures between Celsius and Fahrenheit.
Keep reading
- How Much Water Should a Dog Drink a Day?How much water a dog should drink: about 50 mL per kg a day, a chart by weight, how to measure intake at home and when drinking a lot is a reason to call the vet.
- Does Wet Food Count Toward a Dog's Water Intake?How much water a dog gets from wet food: moisture percent times grams fed, compared with 50 mL per kg, with tables for 5 to 30 kg dogs on wet, mixed and dry diets.
- Why Is My Dog Drinking So Much Water?Why a dog may drink a lot: normal reasons like heat and food, how to measure intake against about 50 mL per kg, the 100 mL per kg line and when to see the vet.
- Feeding Wet and Dry Dog Food TogetherHow to feed wet and dry dog food together without overfeeding: splitting daily calories, worked grams for a 20 kg dog, topper rules and a mixed-feeding table.