NASA’s map that brings together 25 years of clouds

If we use typical clichés with European cities, Seville is the city of the sun and London is the city of rain and clouds, but some get the fame and others take the wool. If the question is where are there more clouds in Europe? NASA has been monitoring the old continent for more than 25 years and has the answer. Spoiler: a long list where, to no one’s surprise, there is also the United Kingdom.

In 1999, NASA launched the Terra satellite, which incorporates the MODIS instrument (medium resolution imaging spectroradiometer). MODIS is, broadly speaking, a sensor that observes the Earth in 36 spectral bands, from the visible to the thermal infrared, which allows it to simultaneously capture temperature, water vapor, aerosols and cloud cover in one pass. Thanks to this combination of bands, MODIS generates cloud fraction products with spatial resolutions ranging from 250 meters to 1 kilometer depending on the channel used.

With data from the year 2000 to 2025 and data released by NASA through its NASA Earth Observations, the Italian data expert and meteorologist Guido Cioni has created this map that solves the question at a glance. There is a clear pattern: northwestern Europe has the most cloud cover on the continent, while the southern Mediterranean enjoys the clearest skies.

The United Kingdom is the country in Europe with the most clouds. Guido Cioni

Beyond the anecdotal, cloudiness has its consequences: directly affects the solar radiation that reaches the earth’s surface, which takes its toll on solar energy production, agriculture, tourism and even health (the vitamin D level of the population). In fact, this map gives us a clue about renewables and why certain European regions depend more on photovoltaic energy and which on wind energy.

The Europe of the clouds and the sunny Europe

Cities such as Bergen in Norway or Glasgow in Scotland appear in intense red, consistent with their rainy climate and direct exposure to the inclement weather of the North Atlantic. The red is softer for Warsaw and Bucharest, two cities in the continental interior, precisely reflecting the continental climate with seasonal but less persistent cloudiness. On the other side of the coin, Seville and Turkish Antalya appear in blue, typical of dry Mediterranean and subtropical climates, and a little behind is Marseille.

That north – south pattern makes sense: Northwestern Europe receives Atlantic storms almost without interruption. The moves are polar jet streamwhich pushes humid air and fronts towards the area and it is these fronts that generate clouds. In Norway, furthermore, the coastal mountains force that humid air to rise, so even more clouds form. Southern Europe experiences just the opposite: there the Azores anticycloneespecially in summer. That is an area of ​​high pressure where the air tends to go down instead of up, and that leaves the skies clear.

Of course, this map and its data have small print: Terra passes through each point on the planet only once a day (around 10:30 local solar time), so this data corresponds to a specific moment, not to a continuous measurement for 24 hours. The good news is that, in 25 years of records, variability and unusual phenomena are cushioned. Furthermore, it only records that specific cloudiness, not the rain: one area may have many high clouds with hardly any rain, and another may have less cloudiness in total but concentrate its rains in short and intense episodes. Finally, NASA explains that in polar areas, distinguishing clouds from snow is a limiting factor that the agency has corrected over time.

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Cover | Gido Cioni