Is my child drinking enough water on hot school days?

The easiest check is the colour of your child's pee: the NHS says most people should drink enough during the day so that their pee is a clear pale yellow. On hot school days children can easily drink too little. In a study of 457 boys in outdoor PE classes at a Bangkok primary school, 20 had an ear temperature above 38°C after exercise, and 18 of those 20 had not drunk any water (an observational finding that cannot show cause). Send a full water bottle every day, make water and plain milk the usual drinks, encourage your child to drink at every break and before and after outdoor play, and learn the signs that a child is getting too hot.

How much should a child drink on a hot school day?

What health agencies say

There is no single number that fits every child, because size, activity and the weather all change how much they need. These guides are a starting point:

The NHS figure of 6 to 8 cups or glasses is a general guide for people overall and counts all drinks, not only water; it is not a number set for children. Separately, a Ramathibodi Hospital @Rama column on food groups for school-age children (6 to 12) includes 2 to 3 glasses (200 ml each) of plain milk a day as part of their meals.

Why pee colour is the practical check

A child cannot see a number of millilitres, but they can look at their pee. The NHS lists dark yellow, strong-smelling pee and peeing less often than usual among the signs of not getting enough fluids. Teach your child to check at school toilet breaks: pale is good, dark means drink more.

What do Thai studies show about children, heat and water?

Findings from Thai studies

What these studies can and cannot tell you

The Bangkok PE study was at one school, included only boys and looked at single lessons, so it shows how quickly children warm up in a Thai PE class rather than how often children become unwell. It is observational, so it cannot show that not drinking caused the rise in temperature. The water study covered rural schools in one area; school water in other places may be different.

What was found in another hot country?

In Israel, Bar-David and colleagues, in a study published in 2009, tested midday urine from 429 children aged 8 to 10 over a week in midsummer. The researchers counted urine below 500 mOsm/kg as a sign of drinking enough, yet 67.5% of the samples were above 800. They describe this as children not drinking enough even when there is water to drink. The study covered one hot, dry region and used midday urine samples, so the figure may differ elsewhere.

Why do children often drink too little at school?

They rely on adults

The US CDC points out that infants and young children rely on others to keep them cool and drink enough when it is hot. The UK Health Security Agency notes that children can be at risk from hot weather because of their bodies, their behaviour and how active they are. The NHS page on coping in hot weather also lists babies and young children aged 5 and under among the people more vulnerable to heat.

Busy breaks and short lessons

Break time is short and play comes first. Children may also not want to queue at a water point or leave the game. A bottle that is with them at their desk and in the playground removes these small barriers.

Uncertain water at school

The Kanchanaburi study shows that school water quality can vary from place to place. If you are unsure, ask the school how its water is filtered and checked; sending a bottle from home makes sure your child has water either way.

How can I help my child drink enough on school days?

Before school

• Give a drink of water or plain milk with breakfast.
• Send a full, clean water bottle that your child can open by themselves. On very hot days or days with PE, a larger bottle or a second bottle helps.

At school

• Agree with your child to drink at every break and at lunch, and before and after PE or outdoor play.
• Tell the class teacher if your child is shy about asking to drink or go to the toilet during lessons.

After school

• Check whether the bottle came home empty. If it is still full, talk about what got in the way.
• Offer water after the journey home, before snacks.

Keep sweet drinks for treats

The NHS says water and milk are the best everyday drinks for children, and the CDC advises avoiding drinks with too much sugar in the heat. For help cutting down sweet drinks, see My child drinks sweet drinks every day. What should I do?

How should children play outdoors on hot days?

Advice for schools that also works at home

The UK Health Security Agency's advice for schools includes:

• children should not take part in vigorous physical activity on very hot days
• loose, light-coloured clothing and wide-brimmed sun hats
• staying in the shade as much as possible outdoors
• sunscreen of at least SPF 30, applied generously and reapplied every 2 hours
• providing water and encouraging children to drink more than usual

The NHS advises avoiding the sun between 11 a.m. and 3 p.m. on hot days. Plan active play for the morning or late afternoon, with shade and water nearby. For how much active play children need, see My child hardly plays actively. How much do kids need?

Never leave a child in a parked car

The US CDC warns never to leave infants or children in a parked car, even with the windows open: the temperature inside can rise by almost 20 degrees Fahrenheit within the first 10 minutes, even with a window cracked open.

What are the warning signs, and when should I get help?

Signs of not getting enough fluids

The NHS lists these signs in adults and children:

• feeling thirsty
• a headache, or feeling dizzy or light-headed
• dark yellow, strong-smelling pee, or peeing less often than usual
• feeling tired
• a dry mouth, lips and tongue
• sunken eyes

Give fluids, with small sips at first if your child feels sick. The NHS advises getting medical advice quickly if a child seems drowsy, feels dizzy on standing that does not go away, is peeing much less than normal, is breathing fast or has a fast heartbeat, or has few or no tears when crying.

Signs the body is getting too hot

The NHS says signs such as tiredness, dizziness, a headache, feeling or being sick, heavy sweating with pale, clammy skin, cramps in the arms, legs or stomach, a high temperature, being very thirsty and irritability are often the same in adults and children. What to do:

1. Move your child to a cool place.
2. Take off unnecessary clothing.
3. Give plenty of water to drink.
4. Cool the skin with cool water and fan them; cold packs wrapped in a cloth under the armpits or on the neck also help.

They should start to feel better within 30 minutes. Stay with them until they do.

Call 1669 straight away if

• your child is still unwell after 30 minutes of resting somewhere cool, being cooled and drinking
• they have a very high temperature
• their skin is hot and not sweating, and may look red
• they have a fast heartbeat
• they have fast breathing or shortness of breath
• they are confused or poorly coordinated
• they have a fit, or pass out

While waiting, keep cooling them with cool water and a fan. If your child has a long-term health condition, ask their doctor for advice about hot weather and activity.