Water and hydration
How much more water does a dog need in hot weather?
Last updated 23 September 2026 · How we write and check this
Short answer
In hot weather, many dogs need 25 to 50 percent more water than their usual baseline, and active dogs outdoors can need close to double. A 20 kg dog normally drinking around 1.1 liters might need 1.4 to 1.7 liters (47 to 57 fl oz) on a hot day, more if walked or exercised.
Why heat raises the number so much
Dogs cool themselves mainly by panting, which evaporates water from the tongue, mouth, and airways at a much higher rate than normal breathing. On a day above roughly 27 C (80 F), especially with exercise, fluid loss through panting alone can rival what is lost through urination.
A rough scaling guide
As a starting point, add about 25 percent to the standard 50 to 60 ml per kg figure for a warm day with normal activity, and consider closer to 75 to 100 percent extra for a hot day combined with exercise or direct sun exposure.
Making sure the extra water gets used
Offer water more often rather than relying on a single large bowl, since heat can make some dogs pant too heavily to drink comfortably in one long session. Bringing water on any outing during hot weather, even a short one, avoids relying on finding a source along the way.
Key takeaways
- Hot weather can raise water needs by 25 to 50 percent or more.
- Panting is the main way dogs lose extra fluid in heat.
- Active outdoor dogs in hot weather may need close to double their baseline.
- Offering water more frequently suits heavy panting better than one large bowl.