If you think the current high temperatures being recorded in several cities across Kenya, including the capital Nairobi, amount to a heat wave, the Kenya Meteorological Department says otherwise.
According to Kenya Met, a heat wave is defined as a period of three or more consecutive days of extremely high daytime temperatures that exceed locally determined thresholds and are linked to increased health risks.
Heat wave thresholds
For cities such as Nairobi, Kisumu, and Mombasa to be classified as experiencing a heat wave, specific temperature thresholds must be met.
In Nairobi, a heat wave is declared when daily maximum temperatures reach 32 degrees Celsius or higher for three or more consecutive days. In Kisumu, the threshold is a daily maximum temperature of 37 degrees Celsius or higher for at least three consecutive days.
Meanwhile, Mombasa would be considered to be experiencing a heat wave if daily maximum temperatures hit 36 degrees Celsius or higher for three or more consecutive days.
According to the weatherman, these thresholds reflect local climate conditions and the observed link between high temperatures and increased hospital visits, admissions and deaths.
“When exceeded, they can be used to trigger heat-health action plans and emergency response measures, particularly to protect vulnerable populations in Kenya’s major urban centres,” the department said.
A 2022 study by the Global Disaster Preparedness Center (GDPC), a Washington D.C.–based initiative of the American Red Cross and the International Federation of Red Cross and Red Crescent Societies, warns that as the climate continues to warm, extreme heat days are increasing globally.
The study notes that hot weather causes hundreds of thousands of excess deaths every year, making extreme heat a growing global public health challenge.
However, it adds that studies examining the link between high temperatures and hospital admissions and deaths, especially in vulnerable regions such as Sub-Saharan Africa, remain limited.
In its findings, GDPC proposed the same heat wave thresholds for Nairobi, Kisumu and Mombasa to guide the issuing of heat-health alerts.
“We use this analysis to propose heat wave definitions for issuing health alert warnings in each city,” the report states.
The organisation says the thresholds can be used to activate emergency response plans and reduce the effects of extreme heat in Kenya’s major economic hubs. It also advises hospitals and medical professionals to closely monitor patients during periods of extreme heat.
At the time of this reporting, the temperature readings for Nairobi stand at 27 degrees Celsius, 30 degrees Celsius for Mombasa, and 28 degrees Celsius for Kisumu.
Can heat waves cause death?
Hot weather is estimated to kill about half a million people worldwide every year.
While heat-related deaths are rarely recorded as the direct cause, extreme temperatures worsen existing conditions such as heart, lung, and kidney disease, leading to early deaths.
Between April and September 2025, much of Europe experienced several severe heatwaves. Record-breaking temperatures appeared as early as April, but the most intense heat began in mid-June, leading to hundreds of heat-related deaths in the United Kingdom.
Temperatures exceeded 46°C (115°F) in Portugal and Spain, setting new national records for June, while at least ten other countries saw regional records broken.
The extreme heat also sparked numerous wildfires, causing widespread damage to ecosystems, property, human life, and air quality across the continent.
Who is most affected?
Heat waves mainly affect children, the elderly, and the sick. Outdoor workers, athletes and emergency responders are also at higher risk due to prolonged exposure.
According to the World Health Organisation, poor communities are often more vulnerable because of poor housing conditions and limited access to cooling.
Protection from heat waves
Health experts advise people to avoid outdoor activities during the hottest hours of the day, stay in the shade, and keep homes cool by closing windows during the day and opening them at night.
Medics also recommend drinking water regularly, wearing light clothing, and checking on vulnerable people in the community.
