After a sweltering, record-setting summer, what do we have to look forward to? Most likely an even hotter one in 2024, meteorologists say, as the El Niño event in the Pacific peaks and warms the globe even further.

As human beings, our survival will depend on our bodies’ ability to regulate our internal temperature.

What Is the Normal Temperature for a Human Body?

A normal body temperature generally lies somewhere between 97.7 and 99.5 degrees Fahrenheit. If our bodies lose control, very bad things may result, including heat stroke, organ failure, and death. But most people take for granted that something guides our temperature up and down as needed.

It’s called the hypothalamus, a little almond-sized knob buried deep inside the brain that monitors body temperature through a network of special temperature-sensing nerve cells. Those on the skin monitor surface temperature, which tends to be a bit lower, while those inside the body monitor core temperature.

The sensors monitor the spinal column, internal organs and brain, through the hypothalamus’ own nerve cells.

Read More: How Extreme Heat Can Kill

How Is Our Body Temperature Regulated?

Everyone has their own “set point” within the above range, and if the body deviates from it significantly, the hypothalamus springs into action.

Too hot? The brain increases sweating, the avenue responsible for about 22 percent of heat loss. We lose most of our body heat through infrared radiation, which the hypothalamus promotes by flooding the skin with warm blood, to cause flushing.

To slow the production of more heat, the brain and thyroid reduce the various chemicals that drive the metabolism. They also encourage physical actions that feel voluntary in the moment, such as taking off clothing and opening up one’s posture to release heat.

The too-cold response involves much of the reverse, including closing up the posture and putting on more clothes.

The body cranks up its metabolism and pulls blood back from the skin, to reduce radiation. And a special part of the hypothalamus, the motor center, triggers muscle contraction and shivering.

Goosebumps may also raise on the skin, but they don’t warm the skin. They are a vestige from when our bodies were covered with dense hair.

Read More: Average Body Temperature Takes A Dip

What Affects Our Temperature?

Despite these mechanisms – and the body’s need for a stable temperature to function properly – the level still varies within a certain range based on exercise and the time of the day.

Other factors can affect body temperature, such as a serious infection, which may prompt the immune system to tell the hypothalamus to temporarily raise the set point. This is called a fever, and it both bolsters the forces of the immune system and slows down those of the invader.

Research has also found that the average human body temperature has varied over time and fallen slightly since the 1800s, when people faced more widespread infections, inflammation and other factors. Men born in the 1990s, the study found, had temperatures 1.06 degrees lower, on average, than men born in the early 1800s.

This may also have been due to living more sedentary lives in cooler, climate-controlled spaces.

Read More: Body Temperatures Today Are Lower Than They Were Two Centuries Ago