Updated: 14 August 2026 la 20:27. Articolul a fost revizuit pentru a reflecta informațiile disponibile la această dată.
A heatwave causes more than discomfort. When temperatures remain high for hours or days, the body must work harder to maintain its internal temperature, while water and salt losses through sweating increase.
The first effects may seem minor: thirst, fatigue, headache, poor concentration or disrupted sleep. In some situations, however, they can progress to heat exhaustion and, in severe cases, heatstroke, a medical emergency.
During periods of extreme temperatures, it is also worth following weather warnings. InfoBuz separately examined Romania’s August 2026 heatwave and the areas most affected, when temperatures in some regions rose towards 39–40°C.
For more information about heatwaves, see also Heatwave in Romania: what to do to avoid ending up in hospital. Temperatures of up to 41°C in the coming period, which provides complementary details on this topic.
Early signs of dehydration
Dehydration occurs when the body loses more fluids than it takes in.
During a heatwave, the main mechanism is sweating. The body releases water to cool down and, if fluids are not replaced sufficiently, the following may gradually occur:
- intense thirst;
- dry mouth and lips;
- darker urine;
- less frequent urination;
- fatigue;
- headache;
- dizziness;
- a feeling of weakness;
- difficulty concentrating.
As a practical rule, the NHS recommends monitoring urine colour: pale yellow urine is generally a sign that fluid intake is adequate, while darker urine and reduced output may indicate dehydration.
When dehydration becomes heat exhaustion
If heat exposure continues, the loss of water and salt can lead to heat exhaustion.
The CDC lists the following symptoms:
- headache;
- nausea;
- dizziness;
- weakness;
- intense thirst;
- heavy sweating;
- irritability;
- elevated body temperature;
- reduced urine output.
The person should be moved to a cool place, unnecessary clothing should be removed, and they may be given fluids in small, frequent sips if they are conscious and able to drink safely.
Warning signs: when to call 112
Heatstroke is far more serious than simple dehydration.
Signs may include:
- confusion;
- slurred speech;
- altered level of consciousness;
- loss of consciousness;
- seizures;
- very high body temperature;
- very hot skin, with or without heavy sweating.
In this situation, emergency medical help must be requested by calling 112, and the person should be moved to a cool place and cooled rapidly until the medical team arrives.
How much water should we drink in summer?
There is no single amount that is right for everyone.
Requirements depend on:
- weight;
- age;
- temperature;
- humidity;
- physical activity;
- diet;
- pregnancy or breastfeeding;
- medication;
- certain illnesses.
Under normal conditions, EFSA considers a total daily water intake of approximately 2 litres for women and 2.5 litres for men to be adequate. Importantly, this total includes water obtained from food, not only glasses of water consumed. Requirements may increase considerably in high temperatures or during physical activity.
During periods of extreme heat, WHO recommends drinking water regularly and indicates, as a general guide, at least approximately 2–3 litres a day for healthy adults, with requirements varying according to circumstances.
Therefore, the rule that “you must drink exactly 2 litres a day” is too simplistic.
Do not always wait until you are very thirsty
During prolonged heat exposure, drinking fluids regularly is more effective than consuming a very large amount at once.
For people doing physical work in the heat, NIOSH recommends, as a guide, about 240 ml of water every 15–20 minutes, which amounts to approximately 0.7–0.95 litres per hour in high-temperature work conditions. These recommendations are intended for occupational heat exposure and do not mean that everyone should consume such amounts throughout the day.
Can you drink too much water?
Yes.
Although dehydration is much more common during a heatwave, consuming very large quantities of water extremely quickly can also become dangerous.
Excessive intake can dilute the concentration of sodium in the blood and cause hyponatraemia.
In the context of working in the heat, NIOSH warns against exceeding approximately 1.4 litres of fluids in one hour, because excessive consumption over a very short period can become a medical emergency.
The risk is more relevant during prolonged physical exertion, when a person sweats heavily and tries to compensate for losses by drinking very large quantities of plain water.
Severe symptoms of hyponatraemia may include confusion, seizures and, in serious cases, coma.
The right approach, then, is not “the more water, the better”, but gradual hydration adapted to fluid losses and activity.
People with kidney disease, heart failure or other conditions for which a doctor has recommended fluid restriction should not arbitrarily increase their water intake.
Plain water or electrolyte drinks?
For most everyday activities and normal heat exposure, water is generally sufficient for hydration.
However, if you sweat heavily for a prolonged period, exercise intensely or do physical work for many hours in high temperatures, the body also loses electrolytes.
For heat cramps, the CDC recommends water along with a snack or drink that can replace carbohydrates and electrolytes.
That does not mean every glass of water you drink in summer needs to be replaced with a sports drink.
Why do we feel so tired when it is very hot?
Fatigue during a heatwave has a physiological explanation.
The body constantly tries to get rid of excess heat. Blood flow to the skin increases and the body produces sweat, a process that places additional strain on the cardiovascular system and kidneys. WHO says heat stress can reduce work capacity and increase the risk of accidents.
If dehydration also occurs, the effect is amplified.
NIOSH says work performance can decline when we are dehydrated even before a person clearly notices it.
There is another important factor:
poor sleep.
If the bedroom remains very warm all night, the body cannot cool down sufficiently, sleep is fragmented and we may feel tired in the morning even if we appear to have slept for seven or eight hours.
Sleeping during a heatwave: how to cool the bedroom
During periods of tropical nights, cooling the home needs to start during the day.
WHO recommends that, when the temperature outside is higher than indoors, windows should be kept closed and shaded with blinds, shutters or external shutters to limit incoming solar radiation.
When the outdoor temperature drops below the indoor temperature, usually in the evening or at night, windows can be opened to release accumulated heat.
This is the exact opposite of keeping windows wide open at 2 p.m. when it is 38°C outside.
For a cooler bedroom:
- close curtains, shutters or blinds exposed to the sun;
- keep windows closed while it is hotter outside than indoors;
- air the home thoroughly in the evening and at night if it is cooler outside;
- turn off computers, televisions and other appliances that generate heat;
- use lightweight bedding and nightwear;
- take a cool shower before bed;
- if possible, sleep in the coolest room in the home.
Especially for infants, people over 60 and people with chronic illnesses, WHO recommends keeping the room temperature ideally below approximately 24°C at night, where possible.
Air conditioning or a fan?
Air conditioning is the most effective way to reduce a room’s temperature when outdoor heat is very high.
A fan does not actually cool the air; rather, it helps the body lose heat through air movement and the evaporation of sweat.
WHO recommends using fans only when the air temperature is below approximately 40°C, as at extremely high temperatures they can contribute to warming the body.
If you use air conditioning during periods of high electricity demand, it is also worth consulting InfoBuz’s article about Romania’s energy alert and the risk of power cuts during periods of high consumption.
Alcohol is not a good hydration solution
During a heatwave, water should remain the main source of hydration.
WHO recommends drinking water regularly during heatwaves and limiting alcoholic drinks.
A very cold glass may seem refreshing, but alcohol should not be used in place of water to make up for losses caused by sweating.
Who is more vulnerable to heatwaves?
The risk is not the same for everyone.
Extra attention is particularly needed for:
- babies and young children;
- older people;
- people with heart disease;
- people with kidney disease;
- people with respiratory illnesses;
- people who work outdoors;
- athletes and people undertaking intense physical exertion;
- people who live alone and do not have access to cool spaces.
For children, the risk is especially important during periods of extreme temperatures, and they should never be left in a parked car, not even for a few minutes.
Europe’s heatwaves show why these measures matter
Episodes of extreme heat are no longer isolated events. In the summer of 2026, several European regions experienced temperatures above 40°C and severe heatwave warnings. WHO warned that extreme temperatures directly affect health and can increase strain on the heart and kidneys.
The European context is explored in greater detail in the InfoBuz article Extreme heatwave paralyses Europe: temperatures above 40°C, alerts and fires.
For the situation in Romania, see also the analysis Heatwave in Romania in early August 2026: the affected areas and how long the heatwave will last.
Mosquitoes and West Nile virus: how to protect yourself in summer and when to see a doctor
Conclusion: proper hydration does not simply mean “drink as much water as possible”
During a heatwave, the body needs help controlling its temperature.
The most important measures are simple:
drink fluids regularly;
do not wait for severe dehydration to develop;
avoid intense exertion during the hottest hours;
keep your home as cool as possible;
protect the bedroom from heat accumulated during the day;
and
quickly recognise the signs of heat exhaustion.
For a healthy adult, daily water requirements cannot be reduced to a single figure. Intake should be adapted to temperature, activity and sweat losses. EFSA indicates approximately 2 litres of total water a day for women and 2.5 litres for men under normal conditions, while requirements rise during heatwaves and physical exertion.
It is equally important not to compensate for losses by drinking enormous quantities of water in a very short time.
If confusion, loss of consciousness, seizures or an extremely high body temperature occur, the problem is no longer one to be solved simply with a glass of water: it may be heatstroke, and emergency medical intervention is needed.
Frequently asked questions
What are the first signs of dehydration during a heatwave?
Early signs may include pronounced thirst, dry mouth, darker urine, infrequent urination, fatigue, headaches, dizziness and difficulty concentrating.
How much water should we drink in summer?
Requirements vary according to age, weight, temperature, physical exertion and health status. On very hot days, it is important to drink fluids regularly and increase intake when you sweat more.
Can you drink too much water?
Yes. Drinking a very large amount of water in a short time can dilute blood sodium levels and cause hyponatraemia. Hydration should be gradual, not based on sudden excessive consumption.
Is plain water enough during a heatwave?
For most people and ordinary activities, water is sufficient. In cases of heavy sweating and prolonged physical exertion, replacing lost electrolytes may also be necessary.
Why do we feel tired when it is very hot?
The body uses energy to maintain its internal temperature and remove heat through sweating and increased blood flow to the skin. Dehydration and poor-quality sleep can worsen fatigue.
How can we sleep better during a heatwave?
It is useful to protect the room from the sun during the day, keep windows closed when it is hotter outside than indoors, and air the room in the evening or at night, when the outdoor temperature falls.
Which is better: air conditioning or a fan?
Air conditioning can actually reduce the room’s temperature. A fan does not cool the air, but helps the body release heat through air movement and the evaporation of sweat.
What are the signs of heat exhaustion?
They may include heavy sweating, dizziness, headache, weakness, nausea, intense thirst and reduced urine output.
When does a heatwave become a medical emergency?
Confusion, loss of consciousness, seizures, very high body temperature and a deterioration in general condition may indicate heatstroke and require emergency medical help.
Who is most vulnerable to extreme temperatures?
Young children, older people, people with chronic illnesses, those who work outdoors and people undertaking intense physical exertion are among the groups at greater risk.
