- Wet-Bulb Temperature and How It Differs from Dry-Bulb Temperature
- How Humidity Shapes Heat Perception and Body Cooling
- The Health Risks of High Wet-Bulb Temperatures
- Mitigation and Adaptation: Keeping Cool in High Heat and Humidity
- Thresholds and What They Mean for You
- Frequently Asked Questions
- Humidity Influences Wet Bulb Levels and Affects Human Well-Being
Wet Bulb Temperature: What Does It Mean in Extreme Heat Waves?
- Wet-Bulb Temperature and How It Differs from Dry-Bulb Temperature
- How Humidity Shapes Heat Perception and Body Cooling
- The Health Risks of High Wet-Bulb Temperatures
- Mitigation and Adaptation: Keeping Cool in High Heat and Humidity
- Thresholds and What They Mean for You
- Frequently Asked Questions
- Humidity Influences Wet Bulb Levels and Affects Human Well-Being
Extreme heat waves are increasing in frequency worldwide, and their impacts have become more deadly. On first look at traditional temperature readings, certain climates may not seem so dire, but this measurement alone doesn’t tell the whole story.
These readings measure dry bulb temperature but don’t take into account wet bulb temperature, a critical measurement for human survival that considers air humidity and how effectively humans can cool themselves off through sweat.
Understanding this metric can save lives during heat waves, so we’re breaking down the term and risks of high wet-bulb temperatures so you can stay safe and healthy.
Wet-Bulb Temperature and How It Differs from Dry-Bulb Temperature
Wet bulb temperature readings use a thermometer wrapped in a damp cloth to measure the potential cooling effect people can experience when sweating to bring down their body heat levels. Dry bulb readings use a standard thermometer to measure the air temperature only.
Wet bulb temperature accounts for humidity in the air and its impact on evaporation, which humans rely on to maintain a safe body temperature, especially in extreme heat.
The lower the wet bulb temperature, the better the cooling potential. In an arid climate, where the air can easily hold moisture through evaporation, it’s easier to cool down and makes the temperature more manageable. In an environment with 100% humidity, the air can’t take on any more water, so sweating becomes ineffective at cooling the body.
For comparison, consider 100ºF with low humidity and 85ºF in high humidity. While 100ºF is startling, a wet-bulb thermometer would show that the 85ºF scenario is actually more dangerous due to the high humidity and its limitations on evaporation.
How Humidity Shapes Heat Perception and Body Cooling
Humidity controls evaporation and changes how heat feels to the body. We use sweat and evaporation to cool ourselves down naturally, but when the humidity of the air is high, it prevents effective evaporation. That’s why an arid climate, like Arizona, and a humid climate, like Florida, create two different experiences at the same dry bulb level.
The arid environment makes the heat more bearable, while the humid climate makes it feel even hotter because we can’t effectively cool ourselves down through sweating. We still produce sweat, but it has nowhere to go.
Regulating your body heat becomes more difficult when the air is saturated with moisture. The “feels like temperature” on a weather app or news report generally reflects wet-bulb conditions and is a more accurate weather reading.
During a heat wave, when the wet bulb temperature approaches our natural body temperature (98.6ºF), it can become dangerous for human health. Because you can’t cool yourself below the wet bulb level through sweating, your body heat will remain elevated until you find a cooler environment, such as an air-conditioned indoor space.
The Health Risks of High Wet-Bulb Temperatures
High wet bulb levels strain the heart, kidneys, and cooling systems of the body. In the above scenario, a high body temperature and heat exhaustion can quickly become heat stroke. Vulnerable groups like the elderly, children, those with chronic health conditions, or outdoor workers are at a greater risk.
Knowing the symptoms of heat stroke allows you to identify those at risk and initiate prompt treatment. Symptoms include confusion, nausea, a rapid heartbeat, and a high body temperature.
Risks of heat stroke are kidney stress due to dehydration, cardiovascular strain from overworking your body’s internal cooling systems, or even death.
Mitigation and Adaptation: Keeping Cool in High Heat and Humidity
When the wet bulb reading is high, you should combine mitigation efforts to avoid extreme temperatures with adaptation strategies to support your body through them.
Cooling technology provides relief, while hydration supports body regulation. Air conditioning is the most effective solution, so find it as soon as possible. During an outage, when HVACs aren’t running, it’s critical to have a backup power station like the EcoFlow DELTA 3 Plus Solar Generator (PV220W) so you can still operate the HVAC or a portable AC unit. Another option is a comprehensive home solar system that automatically switches on to keep your AC running when the grid fails.
If AC is unavailable, use a cold shower or bath to provide immediate relief.
Dehumidifiers can also help reduce indoor moisture levels and decrease the wet bulb reading.
Use sports drinks, coconut water, or electrolyte powders to replace lost electrolytes due to dehydration. Limit outdoor activity during peak heat hours until your temperature has cooled.
Thresholds and What They Mean for You
Remember these wet bulb thresholds so you always know what risks high heat poses.
80ºF wet bulb: Practice extreme caution during prolonged exposure to outdoor temperatures.
88ºF wet bulb: This temperature is dangerous for most people within a few hours.
95ºF wet bulb: The theoretical limit of human survival is six hours maximum.
If you’re about to spend a long time outdoors when the weather is hot, check for these thresholds and prepare or adjust your plans accordingly. Camping, long hikes, picnics, or outdoor events may call for an emergency cooling protocol. One idea is keeping a portable refrigerator, like the EcoFlow GLACIER Classic Portable Refrigerator Freezer, nearby at all times. When AC or a cold bath is unavailable, a portable fridge/freezer can provide cold water, cooling towels, or ice packs to maintain outdoor safety.
Frequently Asked Questions
At What Wet Bulb Temperature Does Heat Become Life-Threatening?
Wet bulb temperatures become life-threatening around 88ºF, and the theoretical survival limit is around 95ºF. These are general thresholds, and individual factors and health can affect each person’s tolerance levels. Avoid wet bulb temperatures above 88°F and seek immediate cooling or medical attention if necessary.
How Does Humidity Affect Wet Bulb Temperature?
Humidity is the primary factor in wet bulb temperature. A higher humidity will increase wet bulb readings, and a lower humidity will decrease wet bulb readings because it allows for significant cooling through evaporation. Dry heat is more survivable than tropical heat.
Humidity Influences Wet Bulb Levels and Affects Human Well-Being
While we often focus on standard temperature readings, which are dry bulb temperatures, wet-bulb readings are a critical survival metric that looks beyond traditional forecasts to understand what the environment actually feels like, considering humidity. The more humid the air, the hotter it feels, and knowing certain wet bulb thresholds allows you to protect your health during bouts of extreme heat. If you live in a humid and hot climate, investing in a backup power source like the EcoFlow DELTA 3 Plus Solar Generator (PV220W) ensures you always have access to powered cooling even if the electric grid goes out. Your health is worth it.