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Since the beginning of wintering, Senegalese have choked under unusual heat. In some regions, the thermometer exceeds 32 °C while the humidity reaches more than 85%. A challenging combination, which makes the air almost breathable and sleep difficult.
Behind this feeling of oppression is a phenomenon still unknown to the general public: wet temperaturean indicator that measures the combined effect of heat and humidity on the human body. However, this parameter can become vital when the climate deregulates, as is increasingly the case in Senegal.
A concept unknown but vital
When talking about heat, one often thinks of the temperature indicated by the thermometer. Yet this figure not telling the whole truth how our body really feels.
What determines our comfort, or our distress, is not only the temperature, but also the humidity of the air.
This is where the notion of wet temperature, or wet-bulb temperature.
It measures the combination of heat and humidityand reflects the ability of the human body to cool by sweating.
Simple principle :
- If the air is dry, the sweat evaporates easily and refreshes the body.
- If air is wet, evaporation becomes difficult: heat remains trapped in the body.
When moisture is too high, our natural cooling system collapses.
Result: body « heating » from within: a phenomenon that can become fatalEven without extreme temperature.
The critical threshold for the human body
Physiological studies show that human beings can no longer maintain their internal temperature (37 °C) when the humid temperature reaches about 35 °C.
Beyond, survival becomes impossible beyond a few hours, even at rest and shade.
👉 But be careful: the danger appears well before this threshold.
From 28 to 30 °C wet temperaturethe risk of heat stroke, exhaustion, dehydration and cardiovascular disorder is becoming high, especially among older people, children, or outside workers.
According to several studies (University of Pennsylvania, NOAA, CNRS), the 35 °C wet bulb temperature is considered as the theoretical limit of human survival.
This corresponds to different combinations of temperature and humidity:
| Air temperature (°C) | Relative humidity (%) | Wet bulb temperature (°C) | Effect on the human body |
|---|---|---|---|
| 30 °C | 70 % | 28 °C | Intense discomfort, abundant sweating, risk of dehydration |
| 32 °C | 75 % | 30 °C | Start of thermal stress, risk for fragile people |
| 35 °C | 60 % | 30 °C | Difficulty in evacuating heat, high risk of exhaustion |
| 37 °C | 70 % | 33 °C | Inefficient sweating, risk of heat stroke |
| 38 °C | 80 % | 35 °C | Limit of human tolerance survival < 6 hours without artificial cooling |
| 40 °C | 50 % | 31 °C | Major risk if physical effort, imperative need for hydration |
| 42 °C | 40 % | 30 °C | Severe thermal stress even at rest |
| 45 °C | 30 % | 29 °C | Extreme hazard, failure of thermoregulation systems |
To be retained
- The human body must maintain 37 °C internal ; Beyond this, the risk of failure increases rapidly.
- High humidity prevents sweat from evaporating, so natural cooling becomes impossible.
- Even at "moderate" temperatures (30–33 °C), a humidity > 70 % may already cause hazardous thermal stress.
Real dramas around the world
🇫🇷 The heat wave of 2003 in France
During the summer of 2003, France experienced temperatures between 35 and 40 °C, with very hot and humid nights.
Result: more than 15,000 deaths in France, 70,000 in Europe.
The heat accumulated in urban housing, combined with high humidity, prevented the human body from cooling. This is a typical example of high wet temperature gone unnoticed.
🇮🇳 India and Pakistan (2015 and 2022)
In recent years, the Indian subcontinent has undergone several extreme heat waves.
In 2022, some areas recorded up to 50 °C, with a moisture content of 60-70%.
The wet temperature above 33 °C, causing thousands of deaths and hospitalization of tens of thousands of people.
Researchers have concluded that Wet bulb reached levels close to human physiological limits.
🇸🇦 Persian Gulf and Middle East
Cities like Doha, Qatar, Dubai, United Arab Emirates or Dhahran (Saudi Arabia) have already experienced, according to satellite measurements, wet temperatures above 35 °C over a few hours; i.e. theoretically invivable without air conditioning.
Outside workers risk death in a few hours without a break or water.
🇲🇽 Mexico and Central America (2024)
An exceptional heat wave caused more than 110 deaths in several Mexican states.
High tropical humidity has amplified thermal stress, causing agricultural losses and electricity cuts due to overconsumption of air conditioning.
And in West Africa: a silent threat
In Senegal, the Gambia or Guinea-Bissau, climate conditions are becoming more and more favourable to episodes of extreme wet heat :
- Temperatures often above 32 °C during the so-called winter season.
- Relative humidity of 80-90% on coastal areas.
- Low wind and dense urbanization, which limit natural ventilation.
These conditions may give wet temperature 28-30 °C, very dangerous if exposure is prolonged.
However, many urban dwellings are poorly insulated, poorly ventilated and without air conditioning, which increases the vulnerability of the inhabitants ; in particular elderly, children and street workers.
The role of climate change
Climate change multiplies and worsens This phenomenon.
Why?
Because a warmer air can contain more water vapour 7 per cent more per degree earned).
Thus:
- The temperatures increase,
- Latmospheric humidity also increases,
- And so the wet temperature climbs ; sometimes faster than air temperature.
Studies show that:
- In South Asia and the Middle East, values of 35 °C wet-bulb already appear on time.
- In West Africa, high thermal stress (beyond 30 °C wet-bulb) 2 to 3 times more frequent by 2050 if global warming exceeds +2 °C.
In other words:
👉 the "wet heat" phenomenon is becoming one of the greatest health risks of the 21st century, especially in tropical and coastal areas.
Human and economic consequences
| Impact | Description | Concrete example |
|---|---|---|
| Health | Heat stroke, dehydration, heart failure, neurological disorders | Death Waves in India (2022), Europe (2003) |
| Productivity | Lower output of outside workers (building, agriculture, fisheries) | Up to –30% effectiveness observed in the Sahel |
| Economy | Loss of working days, cost of care, power outages due to air conditioning | Increase in energy expenditure in urban areas |
| Migration | Movement of populations from too hot coastal areas | Long-term projections for the Gulf and South Asia |
What to do? Prevention and adaptation
Monitor and inform
- Integrate wet temperature orheat index in the weather reports.
- Alert the population when values exceed risk thresholds.
Adapting Our Behaviours
- Avoiding physical effort between 10 a.m. and 4 p.m..
- Drinking regular water (even without thirst).
- Wear clothes clear and comprehensive.
- Se refreshing the skin with water, wet towels, or warm showers.
- Open windows early in the morning and at night, close during the day.
- Search for fresh spaces (health centres, air-conditioned public places).
Action in case of emergency
If a person is present:
- headache, dizziness, confusion, moist or red skin,
- rapid breathing or loss of consciousness, 👉 immediately:
- The shade or in a cool place ;
- Cool body (water, fan, wet linen);
- Call 911.
And in the long term: rethinking our cities and policies
- Urbanism : vegetate cities, create shade zones, encourage natural ventilation.
- Architecture : use clear and reflective materials, promote air circulation.
- Public health : to establish national "heat plans" as in Europe.
- Education Teaching the risks of wet heat in schools and the media.
Conclusion
Heat is no longer just a season, it's a warning.
Every day when the humid breath of air sticks to our skin reminds us that our climate is changing, silently but surely. Behind sleepless nights and suffocating days, it is a message of nature that we must learn to read: our thermal balance, so fragile, is breaking.
The wet temperature thermometer is not a simple scientific instrument; It's the mirror of our vulnerability.
He tells us that the danger comes not only from the sun, but also from the water, the air, and the disorder we sow between them.
In the face of this new challenge, it is no longer just a matter of adapting, but of rethinking how we live, build, produce — and above all, preserve life before it suffocates.
