The brain becomes slower in the heat

The brain also suffers greatly from the heat, and when temperatures exceed 26 degrees its cognitive performance decreases, to the point that we can struggle even to read or explain a graph. 

An important aspect is that the perceived temperature (which combines heat and humidity) matters more than the air temperature. For example, 35 degrees Celsius of dry heat may be better tolerated than 32 degrees Celsius with very high humidity, because sweat evaporates less effectively.

Mental performance is also affected by heat, and in hot environments, many people experience deteriorations, especially in sustained attention; decision-making speed; short-term memory ; and the ability to maintain accuracy. A work or study environment around 20–24°C (68–75°F) is generally considered favorable for cognitive performance; above 26–28°C (80–82°F), performance begins to decline, and above 30°C (86°F), declines become more likely , especially after many hours.

Many cognitive processes depend on temperature , because the brain is an organ extremely sensitive to changes in its internal environment. It's not so much the external temperature itself that influences it, but rather the way it alters body temperature , metabolism, blood flow, and the chemical balance of neurons. Intense heat tends to reduce the ability to sustain attention for long periods. The brain must devote more resources to thermal regulation, and this can leave less "available capacity" for complex tasks.

Under heat stress, sustained attention, complex reasoning, and self-control can become more difficult, so the brain enters "energy-saving" mode. Remember, the brain's energy expenditure is very high: despite representing just 2 percent of body weight, the brain consumes approximately 20 percent of the body's energy. This high energy expenditure, which in the heat produces heat, causes the body to seek self-protection by reducing the energy it expends.

Recent research published in Nature in February 2026 confirmed that even brief exposure to very high temperatures can reduce attention and response speed. Prolonged high heat, however, tends to impair more complex cognitive functions : working memory, planning, situational awareness, and decision-making. Studies under heat stress have observed reductions in advanced cognitive functions when heat and humidity become high.

• To help your brain work better in the heat:
  • drink regularly (even before feeling thirsty);
  • stay in cool environments in the hottest hours;
  • take breaks;
  • avoid very heavy meals when it is very hot;
  • take care of sleep keeping the room as cool as possible.

Read also:

• What happens when we don't sleep because of the heat?
• Record heat: the most effective natural remedies to deal with it
• When you risk heat stress