Paris implemented a temporary ban on public consumption of takeaway alcohol to alleviate pressure on hospitals. This measure followed a four-fold increase in cardiac arrests in the city within a 24-hour period prior to the ban.

Alcohol acts as a diuretic. Estimates indicate that every 1 milliliter of alcohol prompts the body to produce approximately 10 milliliters of urine. For example, a 25-milliliter serving of 40% whisky, which contains 10 milliliters of alcohol and 15 milliliters of water, causes the production of 100 milliliters of urine, resulting in a net water loss of 85 milliliters.

In contrast, a 568-milliliter pint of 5% beer contains about 28 milliliters of alcohol. The alcohol in this quantity of beer stimulates roughly 280 milliliters of urine production, but consuming it leads to a net water gain of approximately 260 milliliters for the body. Professor Ron Maughan, an honorary professor at the University of St Andrews, stated, "You're better off with that pint of beer, you are more hydrated than you would be if you didn't drink it." However, Maughan added, "When you drink not one pint of beer but many pints of beer, you run into difficulties." He also noted, "There's a danger the advice can be counterproductive," and suggested, "You reduce the alcohol content, but maintain the volume."

Hot weather can cause increased sweating, which leads to a loss of water and a subsequent drop in blood volume. Blood vessels near the skin widen in elevated temperatures to help dissipate heat from the blood. Alcohol further causes blood vessels to widen. This combination of heat and alcohol consumption leads to a decrease in blood pressure, requiring the heart to work harder to ensure oxygen reaches the brain and other vital organs.

If the heart is unable to meet this increased demand for oxygen, individuals may experience dizziness and collapse. Dehydration can also cause the loss of electrolytes such as sodium, potassium, and magnesium, which can result in arrhythmias. In severe instances, an insufficient blood supply to the heart can lead to a heart attack. Professor Helmut Seitz, a professor at the University of Heidelberg, commented, "If there is too little blood and the pump function is not good and you have arrhythmia, you may have a problem in supplying your own heart with blood."

Drinking alcohol during a heatwave increases the risk of heatstroke, which occurs when the body fails to regulate its core temperature. Dehydration and alcohol's effects on the brain impede the body's ability to maintain a safe temperature range. Alcohol consumption can also make individuals less likely to recognize heatstroke warning signs, such as slurred speech, headaches, nausea, and a racing heart.

Additionally, alcohol impairs judgment, potentially leading to more aggressive behavior and increased risk-taking. Seitz said, "You risk more than you should do. You jump into the water and break your neck, or jump in and have an infarction [heart attack] because of the shock."