Low clouds can become the worst enemy of someone who wants to see the eclipse on August 12. In the following map, we show the cloudiness forecast for 8 p.m. on Wednesday in each municipality and towards the horizon, as well as the detail of cloud height in each place. The latest available forecast data is from Sunday the 9th; starting tomorrow, Tuesday, the hour-by-hour forecast from AEMET will also be available.
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The cloudiness map is a forecast calculated days in advance, updated every few hours, and its resolution is in kilometers. That is why we provide an indicative assessment: favorable, regular, or unfavorable.
To estimate cloudiness during the eclipse, we combine three prediction models from the European Centre for Medium-Range Weather Forecasts (ECMWF). One indicates how much cloud will be over each point: it is the cloud layer shown colored on the map. Another, AIFS — an artificial intelligence model from the same center — adds a key data point for observing an eclipse: the height of those clouds, whether they are low, medium, or high. The third is HARMONIE-AROME, AEMET’s high-resolution model, which offers an hour-by-hour forecast but not earlier than 48 hours before the event.
This distinction matters because on August 12 the eclipse occurs with the sun very low on the horizon, towards the west-northwest, almost at sunset. That is why it is important to know the cloudiness in each place but also towards the horizon. When looking towards that imaginary line, what blocks the sun are the clouds crossing in that direction. And especially the low clouds, denser and close to the ground. The high clouds (the most common known as cirrus) are thin and often allow the sun to be seen.
It should not be forgotten that there are other elements that can prevent viewing the eclipse, such as the terrain: we show it on this other map.
According to the latest data update, in 86% of Spanish municipalities the clouds will allow a favorable situation to see the eclipse (although it will be total only in the band).
Map Methodology
The map shows a cloudiness forecast for the time of the eclipse at each point in Spain. The visible layer represents the total cloudiness forecast by the European Centre for Medium-Range Weather Forecasts (ECMWF) model, distributed by AEMET through CEPPM. Its approximate resolution is 5 kilometers. From Tuesday, the map will also incorporate HARMONIE-AROME, AEMET’s high-resolution model. Its grid, approximately 2.5 kilometers, allows consulting the cloudiness forecast by specific hours with more local detail than the European medium-range model.
The profiles for each location combine two types of information. On one hand, the total cloudiness forecast at that point by CEPPM, expressed in percentage intervals; and on the other, the average vertical structure of clouds in the municipality according to AIFS, ECMWF’s artificial intelligence model, with an approximate resolution of 25 kilometers (distinguishing between low, medium, and high clouds).
The classification of conditions — favorable, regular, or unfavorable — combines the total cloudiness of the point with the proportion of low, medium, and high clouds forecast over the municipality. The calculation gives more weight to low clouds, intermediate weight to medium clouds, and less to high clouds. The municipal profile does not sum the three AIFS layers: low, medium, and high clouds can coexist at different heights. They are shown as a description of the expected vertical structure, not as mutually exclusive parts of the same 100%.
The “Horizon View” mode is a complementary estimate. It calculates the direction and height of the Sun at the local maximum of the eclipse and takes three samples of low AIFS clouds along the line of sight, at approximate heights between 1 and 2 kilometers. It shows the cloudiest scenario of those samples. It is a guide about possible clouds between the observer and the Sun, not a detailed prediction of terrain or exact visibility.
