How Hot Weather Affects Your Body and How to Stay Safe

How Hot Weather Affects Your Body

Summer heatwaves are more than just uncomfortable — they can pose genuine health risks to people of all ages. While anyone can be affected by extreme heat, certain groups face a higher level of danger. Older adults, babies, young children, and those with underlying health conditions should take particular care during periods of intense heat.

What Happens Inside Your Body When Temperatures Rise

Your body works hard to maintain a core temperature of approximately 37°C at all times, whether you're standing in a blizzard or enduring a heatwave. This is the temperature at which human physiology functions optimally, and your body has evolved over thousands of years to defend it.

When external temperatures climb, your body responds in several ways. Blood vessels near the surface of the skin widen to release heat into the surrounding air. This dilation causes blood pressure to drop, which in turn forces the heart to pump harder to keep blood circulating effectively throughout the body.

Simultaneously, the body begins to sweat. As perspiration evaporates from the skin, it dramatically accelerates heat loss — one of the body's most efficient cooling mechanisms. However, this process also depletes vital fluids and salt, disrupting the delicate balance between the two.

Symptoms Caused by Heat Exposure

Even mild heat exposure can trigger noticeable physical symptoms. Common early signs include an itchy heat rash and swelling in the feet and ankles as blood vessels dilate.

As conditions worsen, the combination of fluid loss and reduced blood pressure can develop into heat exhaustion. This is a more serious condition that demands prompt attention. If blood pressure falls too dramatically, the risk of a heart attack increases significantly.

Should heat exhaustion go untreated, it can escalate into heatstroke, a life-threatening medical emergency requiring immediate intervention.

How to Stay Safe During a Heatwave

The UK Health Security Agency (UKHSA) urges the public to look out for vulnerable individuals — particularly elderly neighbours, people living alone, and those managing chronic health conditions. Prevention is always preferable to treatment when it comes to heat-related illness.

Here are the key steps to protect yourself and others:

• Stay cool indoors by keeping curtains drawn in sun-facing rooms throughout the day
• Hydrate consistently by drinking plenty of water and limiting alcohol consumption
• Avoid peak sun hours — stay out of direct sunlight between 11:00 and 15:00 when UV rays are at their strongest
• Protect yourself outdoors by staying in shaded areas, applying high-SPF sunscreen with a strong UVA rating, and wearing a wide-brimmed hat
• Skip strenuous exercise during the hottest parts of the day
• Never leave children, babies, or animals unattended in a locked vehicle under any circumstances
• Exercise caution near open water — if you're considering cooling off in a river or lake, always check local warning signs and be aware of hidden hazards

What to Do If Someone Has Heat Exhaustion

Knowing how to respond quickly can make a critical difference. If you suspect someone is suffering from heat exhaustion, the NHS advises taking the following steps immediately:

1. Help them lie down in a cool place and gently elevate their feet
2. Encourage them to drink water, or sports and rehydration drinks if available
3. Cool their skin using a spray bottle or damp sponge, fan them actively, and apply cold packs to the armpits or neck

If the person recovers within 30 minutes, heat exhaustion is generally not considered life-threatening.

When to Call 999

However, if there is no sign of improvement after half an hour, the situation may have progressed to heatstroke. This is a medical emergency. Call 999 immediately and continue cooling efforts while waiting for emergency services to arrive. Heatstroke can be fatal if not treated with urgency.