In the summer months it is not unusual for thermometers to exceed 50ºC. However, can we really trust these readings? Is this temperature really accurate? The temperature gauges found on our nation's streets cannot be trusted as an accurate indicator of the day's temperature. When exposed to prolonged sun exposure, they register temperatures significantly higher than the actual measurement.
In this article we are going to tell you if street thermometers measure temperature well and if we can trust it.
Do street thermometers measure temperature well?
Temperature readings provided by various thermometers located throughout the city, including classic free-standing ones as well as those found on bus stop shelters or in vehicles, are known to give inaccurate temperature values.
In addition to direct exposure to the sun, cities introduce another element that contributes to heat: heat emission from asphalt and buildings. Can street thermometers be trusted?
As the sun's energy is absorbed by these urban thermometers, they continue to accumulate heat until they reach their maximum capacity. At this point a reverse process occurs, causing buildings and asphalt to emit heat. This additional heat contributes to the amplification of the temperatures detected by the urban thermometer sensors.
It is important to note that thermometers placed in the sun in urban areas do not serve as accurate temperature reference points. For the most accurate readings, thermometers should be placed in shaded areas and open spaces free of buildings or asphalt, which will allow for better adjustment to the actual temperature.
Street thermometers, due to technical limitations, They do not meet the standards established by the World Meteorological Organization. In contrast, mobile weather apps rely on sources that comply with these regulations.
What is the proper method to measure outdoor temperature?
The measurement of temperature in the street is carried out according to a set of standards established by the World Meteorological Organization (WMO), also known as WMO in English. To ensure accuracy, temperature is measured inside weather boxes, which are wooden structures painted in a waterproof matte white. These boxes are designed with walls arranged in the form of blinds.
The goal is to protect the thermometer from direct sunlight and measure the temperature of the surrounding air, rather than the thermometer itself. By implementing this configuration, the thermometer avoids absorbing moisture during rain while allowing unrestricted airflow.
To guarantee correct placement, the stand must be located at a minimum height of 1,20 meters above ground level, with a free radius of at least 20 meters free of any obstruction. Furthermore, it is essential that the stand be located outside urban centers, with its entrance facing north.
The temperatures indicated by street thermometers cannot be considered reliable since they do not meet any of the necessary requirements.
How does the AEMET measure temperature?
The State Meteorological Agency (AEMET) of Spain measures temperature using a network of meteorological stations distributed throughout the country. These stations are equipped with specialized sensors that capture temperature data accurately and continuously.
The main instrument used to measure temperature is the mercury or alcohol thermometer, which is contained in a meteorological booth. However, currently, these have been largely replaced by electronic sensors due to their greater accuracy and ability to transmit data in real time. These sensors are resistance thermometers or thermistors, which measure temperature based on changes in electrical resistance when the temperature varies.
To ensure that temperature measurements are representative and not influenced by external factors, the sensors are placed inside a weather hut, also known as a weather shelter. This guardhouse is a small white structure that protects the sensor from the sun, rain and wind, while allowing air circulation. The sentry box is generally located 1,5 meters above ground level, an international standard height for measuring air temperature.
The AEMET weather stations record the temperature at regular intervals, which can vary between every 10 minutes and an hour, depending on the season. This data is automatically transmitted to AEMET processing centers, where it is analyzed and validated to ensure its accuracy. If anomalous data is detected, it is manually reviewed to confirm its veracity.
The collected temperature data is used for various purposes, such as making weather forecasts, monitoring extreme weather conditions, and studying long-term weather patterns. This data is also made available to the public, researchers and other institutions for analysis and decision making.
Thermal sensation and street thermometers
In the end, what really matters is the thermal sensation we have and not the number on a street thermometer. While actual temperature reflects the amount of heat in the air, wind chill takes into account other factors that influence our perception of that temperature, such as wind, humidity, and solar radiation.
Understanding thermal sensation It is essential to correctly interpret weather conditions and make informed decisions about how to dress or plan outdoor activities.. For example, a temperature of 10°C on a sunny, windless day may feel comfortable, while the same temperature on a windy day may require warmer clothing.
In winter, low wind chill can increase the risk of hypothermia and frostbite, while in summer, high wind chill can lead to heat stroke or dehydration. For this reason, meteorological services such as the AEMET regularly provide information on thermal sensation along with actual temperatures and this is more important than looking at street thermometers.
I hope that with this information you can know if the street thermometers measure the temperature well or not.