Every day, we check the weather forecast, but do we fully understand all the metrics presented in the weather report?
When discussing climate conditions, it’s important to mention several key factors, not just the ambient temperature. These include: temperature, humidity, wind speed, solar radiation, and UV index. These factors interact closely and can increase or decrease the severity of the surrounding environment.
Understanding Temperature Metrics in Weather Forecasts
Temperature is the most familiar and straightforward metric in weather forecasts. The ideal environmental temperature for the human body is between 20 – 25 degrees Celsius. At this temperature range, the body feels comfortable and operates optimally with little to no disturbances.
The body feels hot when the temperature is 33 degrees Celsius or higher. (Image: CT Sinus Center).
The average skin temperature is approximately 33 degrees Celsius. Therefore, if the ambient temperature is 33 degrees Celsius or lower, the body can dissipate heat effectively without feeling hot. However, when the temperature exceeds 33 degrees Celsius, the body absorbs additional heat from the environment, leading to discomfort.
Weather agencies typically report two temperature metrics: the lowest temperature (at night) and the highest temperature (during midday). The highest forecasted temperature indicates the potential heat stress the body may experience.
Additionally, some applications provide a RealFeel temperature, which reflects the actual (outdoor) temperature that may vary significantly from the forecasted figure. This discrepancy is due to the influence of other factors such as humidity, wind, and sunlight intensity.
Understanding Rainfall Metrics in Weather Forecasts
Rainfall measures the amount of precipitation received after each rain event. Rainfall is quantified based on the volume of rain collected on a flat surface that is not obstructed by buildings or vegetation, measured in millimeters (mm).
A rainfall measurement of 1 mm means that the volume of rain collected on one square meter of flat ground is 1 mm deep after rainfall. Therefore, if a rainfall of 200 mm is recorded, it indicates that the water would cover 200 mm on one square meter of land (assuming the ground does not absorb water). In reality, some water will seep into the ground and flow into rivers, so we rarely perceive the actual rainfall amount unless during heavy downpours.
In Vietnam, there are about 100 rainy days each year, with average rainfall ranging from 1,500 to 2,000 mm, distributed unevenly. Across Vietnam, approximately 600 billion tons of rainwater falls annually, equivalent to around 20,000 tons per hectare, primarily concentrated during the rainy season.
Understanding the UV Index in Weather Forecasts
The UV index is an international standard measurement of the intensity of ultraviolet rays reaching the Earth’s surface, designed to assess the level of UV radiation at a specific location on a given day.
This index aims to advise the public on appropriate protective measures, as excessive exposure to sunlight can cause sunburn, eye damage such as cataracts, skin aging, immune system suppression, and skin cancer.
It’s advisable to protect yourself when going out on sunny days to safeguard your skin. (Image: Anitasfeast).
The UV index ranges from 1 to 11+, displayed from low to high in colors such as green, yellow, orange, red, and purple, accompanied by relevant recommendations.
UV index ranges from 1 to 11+.
Understanding Humidity Metrics in Weather Forecasts
Humidity is a physical quantity that indicates the amount of water vapor present in the air; it is an essential characteristic of weather and climate. According to researchers, humidity is divided into two types: absolute humidity and relative humidity.
Absolute humidity refers to the amount of water vapor in a given volume of air, measured in mg of water per cm³ of air. However, in practice, absolute humidity does not provide specific information as it is not related to the air’s evaporative capacity.
Relative humidity is expressed as a percentage (%), with 100% relative humidity indicating that the air is saturated with water vapor.
High humidity for extended periods can lead to cold-related illnesses. (Image: Blog – Reliance Home Comfort).
Vietnam has a tropical humid climate, where relative humidity can be very high (90 – 100%). High humidity also reduces the body’s ability to sweat, causing feelings of heaviness, fatigue, and lethargy. Prolonged periods of high humidity can lead to cold symptoms and flu.
In areas with high humidity (tropical rain), the air is continuously moist and contains a high density of bacteria, which can cause discomfort, mold growth, and damage to wallpaper. This can lead to respiratory illnesses, fever, and digestive diseases in both humans and animals. High humidity also affects the functioning of electrical and electronic devices.
Conversely, as temperatures rise and the weather warms, humidity levels in the air will decrease to a certain extent. When humidity drops too low (in polar regions, deserts, or high mountains), individuals may suffer from dehydration, leading to dry, cracked skin and discomfort, while the resistance of flora and fauna also diminishes.
Both low and high humidity can significantly impact human life, making it essential to maintain humidity at an appropriate level.
According to researchers, the ideal humidity level for human comfort is around 50-60%, facilitating the sweating process and making individuals feel comfortable and refreshed.
Understanding Dew Point Metrics in Weather Forecasts
The dew point of a given air mass, at a fixed atmospheric pressure, is the temperature at which the water vapor in the air mass condenses into liquid water. In other words, the dew point is the temperature at which the relative humidity of the air mass reaches 100%.
The dew point determines the relative humidity. When relative humidity is high, the dew point is close to the current air temperature. If relative humidity is 100%, the dew point will equal or exceed the air temperature at that time. If relative humidity decreases, the dew point will be lower for the same air temperature.
People accustomed to a typical continental climate begin to feel uncomfortable when the dew point reaches around 15° – 20°C. Most individuals living in such areas find a dew point above 21°C to be oppressively humid.
