The Met Office has extended its amber extreme heat warning to cover both Monday and Tuesday, with forecasters predicting temperatures could reach 37 degrees Celsius across parts of England and Wales. The warning, initially set to run from Monday 22 June through Thursday 25 June, now covers the early part of the week, with highs of 36 to 37°C expected in some areas and the possibility of record-breaking June temperatures. The current June record of 35.6°C – set in Southampton in 1976 and Camden Square in 1957 – may be challenged, according to the Met Office.
Health experts are warning that such extreme conditions pose significant risks, particularly for those with underlying health problems. Robert Bradshaw, Superintendent Pharmacist at Oxford Online Pharmacy, said high temperatures and humidity can be a dangerous combination for anyone who suffers from high blood pressure. “The hot weather causes the heart to beat faster, circulating twice as much blood around the body,” he explained. This increased cardiovascular demand places additional strain on the heart and circulatory system, making it harder for the body to regulate its core temperature.
Certain medications commonly prescribed for hypertension and other conditions can further compromise the body’s ability to cope with heat. Mr Bradshaw highlighted that beta blockers and diuretics – including water tablets such as furosemide – may reduce the body’s capacity to maintain proper hydration or respond to intense heat. The Medicines and Healthcare products Regulatory Agency (MHRA) and pharmacists have urged extra caution, noting that heat can break down active ingredients in many medicines, rendering them less effective unless stored below 25°C. Refrigerated medicines such as insulin are particularly vulnerable.
Other blood pressure medications, including ACE inhibitors and calcium channel blockers, can impair temperature regulation, suppress thirst responses, or slow circulation, making it harder to cool off. Mr Bradshaw stressed that patients should not stop taking prescribed medication without consulting a healthcare professional, but should instead take preventative measures and discuss concerns with their GP or pharmacist.
For those with high blood pressure, the pharmacist recommends consuming ample fluids, seeking cool environments, and wearing protective headwear when outdoors. Regular monitoring of blood pressure throughout the heatwave is essential, he said. Symptoms that warrant immediate emergency medical attention include severe fatigue, confusion, rapid heartbeat, excessive perspiration, headaches, limb swelling, or nausea.
Vulnerable groups and medication risks
The amber warning highlights potential health impacts for the wider population, not just those traditionally considered vulnerable. However, certain groups remain at higher risk: individuals aged 65 and over, babies and young children aged five and under, pregnant women, those with serious mental health problems, and people with underlying conditions such as heart problems, breathing problems, dementia, diabetes, kidney disease, Parkinson’s disease, or mobility problems.
In addition to blood pressure drugs, other common medications can increase risks during a heatwave. Antidepressants, including SSRIs and tricyclics, can impair the body’s internal thermostat by altering neurotransmitters, limiting the ability to sweat. Antipsychotics can block dopamine and alter serotonin, disrupting the hypothalamus – the brain’s temperature regulator – leading to reduced sweating and a failure to recognise overheating or thirst. Stimulant medications for attention disorders can increase body temperature. Anticholinergic medicines, including some antihistamines (e.g., diphenhydramine), medications for urinary incontinence (e.g., oxybutynin), and some antidepressants (e.g., amitriptyline), can directly suppress the body’s ability to cool itself by reducing sweat production.
Diabetes medications also require attention. Insulin can become unstable if not stored correctly, and dehydration can disrupt blood sugar levels. Symptoms of dehydration can mimic low blood sugar. Metformin increases the risk of dehydration or makes its early symptoms harder to spot. The MHRA advises people to store all medicines below 25°C where possible, and to keep refrigerated medicines like insulin in a cool bag if travelling.
Dehydration and hydration advice
Dehydration is a serious concern when temperatures climb, particularly for those spending extended periods in direct sunlight. Under normal circumstances, adults should consume between 1.5 and 2.5 litres of fluid daily – equivalent to roughly six to eight glasses – a requirement that increases substantially during hot weather as perspiration accelerates water loss. Mr Bradshaw warned that dehydration can leave you feeling extra thirsty, tired, or dizzy, and cause headaches, constipation, or nausea, as well as dark, strong-smelling urine.
He advised maintaining consistent fluid intake throughout the day, matching water consumption with other beverages, and restricting alcohol due to its diuretic properties. Oral rehydration sachets containing electrolytes such as glucose, sodium and potassium can prove particularly beneficial, helping replenish lost salts and mitigate dehydration’s effects. Severe dehydration – characterised by confusion, rapid heartbeat, low blood pressure, fainting, sunken eyes, or a lack of tears in infants – requires immediate medical attention.
Insect bites, prickly heat, and other summer ailments
Warmer weather inevitably brings increased insect activity, and with more people venturing outdoors, the likelihood of stings and bites rises considerably. Such incidents typically cause a brief, sharp sensation followed by localised swelling. Mr Bradshaw advised checking the affected area for any remnants of the insect before treatment. Antihistamines can alleviate itching, while steroid creams reduce inflammation. Repellents containing DEET offer effective protection. Should symptoms escalate to include dizziness, stomach pain, fever, swollen glands, or allergic reactions, medical assistance should be sought without delay.
Prickly heat, caused by excessive perspiration irritating the skin, presents as clusters of itchy red spots commonly appearing on the neck, chest, armpits, and waistline. Loose cotton garments help prevent the condition, while pharmacists can recommend treatments including antihistamine tablets, hydrocortisone cream, and calamine lotion.
The Met Office has also warned of potential thundery downpours on Monday and Tuesday, though these are expected to be isolated. The heatwave is notable for its high humidity, with dew points around 22°C forecast for Wednesday and Thursday, making conditions feel oppressive and exacerbating heat stress. Consecutive nights where temperatures do not drop below 20°C – so-called tropical nights – are also predicted, particularly in urban areas, making it difficult for people to recover from the daytime heat.
Separately, the RNLI has warned of an increase in potential water safety incidents as more people visit coastal areas, lakes, or rivers. Cold water shock remains a significant danger even in warmer weather, as sea surface temperatures are not yet as high as in mid-summer. The RNLI advises people to enter the water slowly and to “Float to Live” if they find themselves in difficulty.
Heat stroke prevention – the gravest threat
Heat stroke poses perhaps the gravest threat during extreme temperatures, developing within hours when physical exertion or prolonged exposure overwhelms the body’s cooling mechanisms. Those at heightened risk include individuals who are dehydrated, consuming alcohol, taking certain medications – including sedatives and heart drugs – or living with conditions such as cystic fibrosis or cardiac problems.
Warning signs encompass delirium, weakness, flushed skin, nausea, and vomiting. Untreated cases can result in brain swelling, organ failure, or nerve damage. The body’s temperature regulation fails, leading to a dangerously high body temperature of over 40°C. Symptoms include confusion, lack of coordination, hot and dry skin (though it can also be profusely sweating), rapid heartbeat, seizures, and loss of consciousness.
Prevention centres on limiting physical activity, staying hydrated with water or sports drinks, seeking shade, and wearing lightweight clothing. If someone is suspected of having heat stroke, Mr Bradshaw advised: “While you’re waiting for assistance, apply ice packs to the neck, groin and armpits, immerse them in cool water, encourage them to drink water and monitor their breathing.” Immediate first aid involves moving the person to a cool place, removing excess clothing, calling 999 or 111, wrapping them in a cool wet sheet, and continuously pouring cold water over it. Fanning or sponging them with cool water helps. Cooling should continue until their temperature drops to around 38°C. Crucially, aspirin and paracetamol should be avoided during heat stroke episodes.