Should You Drink Cold Water When You're Hot? The Surprising Science

November 17, 2025 •

4 min read

According to a 2013 study, drinking cool tap water (~16°C) may be the optimal temperature for rehydration in dehydrated athletes. This often contradicts the common impulse to grab ice-cold water on a scorching day, raising the question: should you drink cold water when you're hot?

Quick Summary

This article explores the physiological effects of drinking cold water when overheated, detailing its benefits for rapid cooling and potential trade-offs regarding hydration. It addresses common myths, compares temperature options, and provides practical advice for effective heat management.

Key Points

Immediate Cooling: Drinking cold water provides an immediate internal cooling sensation by acting as a heat sink, absorbing heat from your body as it warms up to your core temperature.
Improved Performance: During intense exercise in the heat, drinking cold water can help lower your core body temperature, which may help improve endurance and delay fatigue.
Potential Drawbacks: For some people, cold water can cause headaches, aggravate digestive issues, or slow down overall fluid absorption compared to moderately cool water.
Optimal Rehydration: Research suggests a water temperature of around 16°C (cool tap water) may be optimal for maximizing voluntary fluid intake and absorption, especially for dehydrated athletes.
Personal Preference Matters: The most crucial factor for hydration is consistently drinking enough fluids. The best water temperature is the one that you find palatable enough to drink regularly.
Listen to Your Body: Pay attention to how different water temperatures affect your body. If you experience discomfort from cold water, switching to a cooler or room-temperature option is a valid choice.

The Science of Cold Water and Body Temperature

When your body is hot, its primary goal is to cool down. It does this by sweating and by moving blood closer to the surface of the skin to dissipate heat. The temperature of the fluids you consume interacts directly with this internal system, creating a cooling effect, but the process is more complex than simple thermodynamics. When you ingest cold water, it acts as an internal 'heat sink,' absorbing heat from your body as it warms up to core temperature. This can lead to a rapid, internal cooling sensation that is both refreshing and effective for lowering your core temperature, especially in extreme heat or during intense exercise.

Cooling vs. Sweating: A Delicate Balance

Interestingly, some studies show that while cold water ingestion provides internal cooling, it can also stimulate thermoreceptors in the stomach that lead to a slight decrease in the sweating response. For environments that are both hot and humid, this might not significantly impact overall cooling, as sweat would drip off the skin anyway. However, in hot, dry, and windy conditions, reducing sweating can actually decrease overall evaporative cooling, potentially negating some of the benefit. For most people in hot conditions, the immediate relief and internal cooling offered by cold water are the primary benefits.

The Arguments Against Cold Water: Fact vs. Myth

Despite the immediate gratification, several myths and some minor downsides are associated with drinking cold water when hot. Many of these claims are exaggerated, but understanding the real potential issues is important.

Potential Drawbacks to Consider

Digestive Discomfort: Some traditional practices suggest that cold water can constrict blood vessels in the digestive tract, hindering digestion. While this is not a major concern for healthy individuals, people with sensitive stomachs or pre-existing digestive issues might experience some discomfort.
Headaches: For individuals prone to migraines, drinking very cold water, especially quickly, can sometimes trigger a headache. This is often due to the temperature change affecting nerves in the head and throat.
Slower Hydration Absorption: Some research indicates that the body processes and absorbs room-temperature or slightly cool water more quickly than ice-cold water. This is because the body must first expend energy to warm the liquid, which can slightly delay overall hydration. For athletes needing rapid rehydration, a moderately cool temperature might be more effective.

A Comparison of Water Temperatures When Overheated


Feature	Cold Water (e.g., 5°C / 41°F)	Cool Water (e.g., 16°C / 60°F)	Room Temp Water (e.g., 26°C / 79°F)
Cooling Effect	High. Provides rapid, immediate core temperature reduction.	Moderate. Less rapid than ice-cold, but still helps cool the body.	Low. Primarily cools via evaporative sweating, not direct ingestion.
Rehydration Speed	Slower. The body must warm it up, potentially slowing absorption.	Optimal. Research suggests this temperature encourages higher voluntary intake and faster absorption for rapid rehydration.	Fastest (Theoretically). Processed quickly by the body without major temperature adjustment.
Palatability	High. Many find it most refreshing and appealing, especially in intense heat, encouraging higher intake.	Moderate to High. A pleasant and palatable temperature for many, leading to higher consumption than colder water in some studies.	Lower. Can feel less satisfying and less thirst-quenching than cooler water in hot conditions.
Athletic Performance	Enhances Performance. Effective for lowering core temperature during intense exercise, which can reduce fatigue.	Highly Recommended. Some studies suggest this may be the best for effective rehydration in athletes after exercise.	Neutral. Primarily effective for general hydration, less so for active cooling.
Best Used For	Intense heat exposure, physical exertion, immediate cooling.	Rapid rehydration post-exercise, general hydration in warm conditions.	Everyday hydration, gentler on sensitive digestive systems.

Making the Right Choice for Your Situation

Ultimately, the 'best' water temperature depends on your specific needs and personal comfort. For most healthy individuals, the potential drawbacks of drinking cold water when hot are minor compared to the benefits of staying hydrated. The most critical factor is simply drinking enough water, regardless of temperature, to replenish fluids lost through sweating. However, there are some nuanced situations to consider.

When to Prefer Cold Water

During or after strenuous exercise: Drinking cold water can help lower your core body temperature and increase endurance in hot conditions.
In extreme heat or high humidity: When your body's natural evaporative cooling is less efficient, drinking cold water provides an effective internal cooling mechanism.
To increase alertness: The shock of cold water can provide a quick, non-caffeinated energy boost by stimulating adrenaline production.

When to Consider Cool or Room Temperature Water

For maximum rehydration efficiency: If rapid fluid absorption is the primary goal, especially after dehydration, cool water (around 16°C) may be more effective, as it doesn't cause the body to slow intake.
If you have a sensitive stomach or esophageal issues: Individuals with achalasia or digestive sensitivities might find room temperature water easier to tolerate.
For optimal daily hydration: If drinking cold water discourages you from consuming enough water due to discomfort, opt for a temperature you find palatable and will drink consistently.

Conclusion

For most people, the immediate relief and internal cooling from drinking cold water when hot are perfectly safe and effective. It helps manage core body temperature and can even boost exercise performance in hot conditions. While some minor drawbacks exist, like potential for headaches in sensitive individuals or slightly delayed absorption, they are generally outweighed by the benefits of hydration. Ultimately, the best strategy is to prioritize consistent fluid intake and choose the temperature that you are most likely to drink consistently, listening to your body's individual needs. For rapid rehydration, a cool temperature might be marginally better, but staying hydrated in any way you can is the priority. For more information on maintaining fluid balance, consult the guidelines at the Gatorade Sports Science Institute.

Note: The most important rule of hydration is to drink consistently, and the best water temperature is the one that encourages you to do so regularly.

Frequently Asked Questions

No, it is not dangerous for most healthy people. The idea that it can cause strokes or major shock is a myth. While it can cause minor issues like headaches in sensitive individuals, the practice is safe and can be beneficial for cooling down.

Some traditions suggest cold water restricts blood vessels in the digestive tract. While there's limited evidence for major harm, it can slightly slow down the digestive process as the body works to warm the water. For most people, this effect is negligible.

Yes, some studies show that cool water, around 16°C (60°F), is absorbed more effectively and encourages people to drink more volume compared to ice-cold water. This can lead to more efficient rehydration, especially post-exercise.

For individuals with a history of migraines, drinking ice-cold water quickly can sometimes trigger a headache. This is typically due to a sudden change in temperature affecting the nerves in the throat and sinuses.

The ideal temperature is largely a matter of personal preference. Cold water is excellent for rapid cooling and can encourage more drinking. However, moderately cool water is often optimal for efficient rehydration. Most importantly, drink whatever temperature encourages you to drink enough water consistently.

The body expends a small amount of energy to warm cold water to your core body temperature, resulting in a negligible increase in calories burned. This effect is minimal and not a viable weight-loss strategy.

The notion that cold water harms the immune system by thickening mucus is largely based on tradition rather than robust scientific evidence. While some find warm water soothing for cold symptoms, there is no strong evidence that cold water impairs immune function in healthy individuals.