Persistent night sweats, even during warm weather, could be an early sign of cancer and should not be ignored, according to Dr. Jiri Kubes, a radiation oncologist at the Proton Therapy Centre. While hot temperatures commonly cause discomfort at night, Kubes warns that unexplained, drenching sweats warrant medical attention.
Cancer Research UK notes that about one in three individuals delay seeking medical advice for six months after noticing potential warning signs. These symptoms, which can also include fatigue, persistent itching, changes in appetite, and bloating, may be attributable to various health issues or environmental factors, but can also indicate serious illness.
"The important distinction is whether there is an obvious explanation," Dr. Kubes stated. "In the case of night sweats, if the room is cool but you are repeatedly waking with your pyjamas soaked through, that is different from simply feeling clammy on a hot night."
Drenching night sweats are particularly associated with certain types of blood cancer, such as lymphoma. These cancers arise from abnormal blood cells that multiply, hindering the function of healthy cells. In the UK, over 41,000 people are diagnosed with blood cancer annually, yet fewer than half of adults can identify a single symptom.
While symptoms can vary, frequent and severe night sweats, along with fatigue and recurring infections, are common indicators of blood cancer. Dr. Kubes advises that if unexplained night sweats continue regularly for more than two to three weeks, it is advisable to consult a general practitioner. He also stressed that individuals experiencing severe sweating or other concerning symptoms should seek advice sooner, without waiting several weeks.
Other potential symptoms of blood cancer include unexplained bruising, bleeding, bone or joint pain that disrupts daily activities, significant weight loss, shortness of breath, and persistent itchy skin. Swelling in the neck, armpit, or groin that is painless can also be a cause for concern.
However, Dr. Kubes emphasized that cancer is not the most frequent cause of night sweats. Numerous other factors can contribute, including menopause, anxiety, an overactive thyroid, alcohol consumption, and certain medications like antidepressants, steroids, and some painkillers. Similarly, fatigue is common during heatwaves but becomes more concerning when prolonged, severe, and accompanied by symptoms like drenching sweats, fever, or weight loss.
Dr. Kubes's advice is to recognize persistent, unexplained changes, especially when other warning signs are present. He urges individuals not to wait for the weather to cool if sweating is severe, persistent, or accompanied by other symptoms.
Britain has experienced its fifth heatwave this summer, with temperatures reaching high levels. The UK Health Security Agency (UKHSA) issued a heat health alert, warning of increased mortality. In May and June of this year, deaths linked to extreme temperatures in Britain were nearly double the entire figure for 2025. Dr. Ross Thompson, Principal Environmental Public Health Scientist at UKHSA, highlighted the dangers of extreme weather, particularly for vulnerable populations such as older adults and individuals with pre-existing health conditions.