How Hot Weather Affects Your Health – and What to Watch For

When temperatures climb, your body works harder than you most people realise. Keeping a safe core temperature is a full-time job for your heart, lungs, and kidneys, and hot weather makes that job a lot tougher.

Your heart pumps faster to push blood towards your skin, where heat can escape, and you sweat more, losing fluid and essential salts.

Most healthy people won't notice this extra effort, but it still puts extra strain on the body – and for some, it can become genuinely dangerous.

Here’s what you need to keep in mind.

Who needs to take extra care in the heat?

Hot weather doesn't affect everyone equally. It's worth taking a moment to think about whether you, or someone you care about, falls into one of these groups:

• Over 65s – the body's ability to regulate temperature naturally declines with age, and older adults often feel thirst less strongly, so dehydration can creep up unnoticed.
• People with heart conditions – the heart is already working harder in the heat, so anyone with high blood pressure, angina, or heart failure is under extra strain.
• People with kidney problems – fluid loss concentrates the blood and forces the kidneys to work harder than usual, which can worsen existing kidney issues or trigger new ones.
• People with diabetes – heat can affect blood sugar control and increase the risk of dehydration.
• People on certain medications – diuretics ("water tablets"), some blood pressure medicines, and certain mental health medications can all affect how the body handles heat and fluids.
• Young children and babies – small bodies heat up faster and can't always tell you how they're feeling.
• Anyone working or exercising outdoors – even the fit and healthy can sometimes underestimate the effects of the heat.
• Pregnant women - Increased risk of preterm birth and dehydration; heat regulation is impaired in pregnancy
• People with respiratory conditions (asthma, COPD) - Heat exacerbates airway inflammation; also relevant in UK context alongside air quality deterioration during heatwaves

Symptoms to know, and numbers worth checking

Dehydration is usually the first sign of trouble: thirst, a dry mouth, dark yellow urine, headaches, dizziness, and fatigue.

By the time you feel thirsty, you're already mildly dehydrated, so try to sip water regularly throughout the day rather than waiting until you're thirsty.

Heat exhaustion brings heavy sweating, clammy or pale skin, cramps, nausea, a rapid pulse, and faintness. If this happens, make sure to move somewhere cool, lie down, drink water, and try to cool your skin with damp clothing or a fan. Most people recover within 30 minutes.

Heatstroke is a medical emergency. Symptoms include a very high temperature, hot dry skin, confusion, slurred speech, or loss of consciousness. Make sure you call 999 immediately.

Beyond these immediate warning signs, hot weather is also a good moment to check in on the numbers behind your health:

• Blood pressure – heat causes blood vessels to widen, which can drop blood pressure and cause dizziness or falls, particularly if you're on medication. If you monitor at home, keep a closer eye on your readings during a heatwave.
• Kidney function – repeated dehydration puts real stress on the kidneys. Markers such as creatinine and eGFR reveal how well they're coping, long before symptoms appear.
• Heart rate and rhythm – a persistently racing or irregular pulse in hot weather shouldn't be ignored.
• Blood sugar – if you're diabetic, check more frequently, as heat can send levels in either direction.

Why a heatwave is a good time for a health check

If you have a health assessment booked during a warm spell, it might be tempting to put it off – but it's actually one of the best times to get checked.

Many of the risks above are invisible day to day: raised blood pressure, declining kidney function, and early heart strain rarely announce themselves until they cause a problem.

A health assessment can help measure exactly these things, giving you a clear picture of how well your body is coping with the heat, and with everything else.

Knowing your numbers means you can spot potential issues early, make informed changes if needed and enjoy the summer with a little more peace of mind.

Small things that help

A few simple habits can make a real difference in the heat: staying out of the sun between 11am and 3pm, drinking water regularly, and going easy on alcohol and caffeine.

Loose, light-coloured clothing and a hat help too, and closing the curtains on sun-facing windows keeps your home cooler for longer.

It's also worth checking in on elderly neighbours, friends, and relatives, who may not always realise they're becoming dehydrated or overheating.

Hot weather can be a real joy, but it puts more demands on your body than you might think. So, make sure you know the warning signs and you’ll be able to enjoy the sunshine with confidence – instead of worry.

If you're curious what your own numbers say, a Bluecrest Health Assessment is a good place to find out.

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Need help? Call free on 0800 652 2183 to speak to one of our team.