Spain became a bakery. Temperatures have reached 44 degrees in some parts of the country and there is no fan to save us from this unbearable heat. Suffice it to say that the authorities have raised the orange alert (significant risk) in 32 provinces of the communities of Aragon, two Castiles, Catalonia, Madrid, Navarra, the Basque Country, La Rioja and the Valencian Community.

We can all say firsthand that it’s hot, but there’s something shocking about the numbers street thermometers show us: they’re not the same ones that appear on our mobile phones. One says they do 50º, the other says it doesn’t exceed 40º. Why? Why? Which one should you pay attention to?

argument. A few days ago, journalist Fermin Grodira said on Twitter He said he saw a marquee on the street marked 58°C. “These thermometers are giving false information that something needs to be done at the enterprise level,” he said. Jesús González Alemán, PhD in Physics and Meteorologist from AEMET, commented: “Deniers are using old images of thermometers reading 40º on the street to oppose climate change. So let’s lower ourselves to the same level.”

They are not misguided. These values ​​are not real and the figures they show are exorbitant given their location and the materials they use. They are often metallic, dark in color and exposed to the sun most of the day, so they are not a reliable reference.

Explanation. First of all, it should be noted that these thermometers not only receive long hours of sunlight, as we see at bus stops, but also absorb the extra heat given by buildings and asphalt. Although they can measure temperature more or less well in the early morning hours, their reliability is greatly reduced during the hot afternoon hours. Why? Why? Due to overheating of the device system itself.

That is, after a certain time, the thermometer will no longer measure the temperature of the air in the street, but the temperature of its own metal plate, which by that time will practically “burn out”.

Problems. All of this makes us wonder if it still makes sense to continue practicing. This article in La Vanguardia talks about how this can lead to psychological danger: Seeing a thermometer show a temperature above 45º (even if it’s wrong) can cause a feeling of suffocation, especially in older people.

Not only that, it’s a major disinformation tool, both on social networks where images of urban thermometers are shared, and in the political arena: We’ve seen multiple ministers display photos of them to defend certain ideas.

AEMET does not measure it that way. The same State Meteorological Agency argues that we should not pay too much attention to the images of the poles circulating on social networks. In a report we published on Magnet years ago, Javier Rodríguez, head of the operational forecasting area of ​​AEMET, told us, “It’s not that the sensors of these devices are bad, it’s that they don’t meet the warranty requirements. The data that reflects is correct.” In order to pass a minimum reliability standard, it refers to the fact that the device is “inside a meteorological shelter, in the shade, at an altitude of one and a half meters from the ground and has some ventilation.” What we see every day does not fit.

In addition, the fact that the boxes used by AEMET are not metal but wood increases reliability. But above all, theirs are located outside the city or near airport areas, where the measurement conditions required by WMO can be easily reproduced. You can read more about how these metrics work. here.

And where does Google get the information from? The American company gets its weather information from: Air Underground. It is a platform that includes stations from all over the world. And unlike the thermometers we see at bus stops, all of these stations comply with WMO standards. Even on the same Weather Underground page, we can see and check how they are. all stations associated with your data sources.

With all that said, the answer to where we have to go to know the actual temperature is pretty obvious. It’s better to look at the clock on a cell phone than at the marquee on duty. And no, the 50ºC thing right now is a fantasy. for now