When observing a low-altitude solar eclipse, like the one that will occur in Spain on August 12, 2026, it is possible for distant clouds to obstruct the view. The sun will be at a low angle on the horizon during this eclipse. In Mallorca, for instance, the Sun will be at an altitude of only 2.4° above the horizon during totality. This means that the distance and height of clouds can greatly impact your ability to see the event
Cloud Types and Height
Clouds are categorized by their height:
High clouds are found between 7 and 12 kilometers and are made of ice crystals. Cirrus clouds are an example of high clouds.
Middle clouds, such as altocumulus, are located between 2 and 7 kilometers.
Low clouds are found up to 2 kilometers in height. Stratus clouds are an example of low clouds and often bring drizzle.
The cumulonimbus is a significant cloud type because it can extend across all heights, from the ground up to 12 kilometers. This type of cloud is associated with thunderstorms and it could be the enemy number one for a late summer afternoon eclipse.
The Sun's Altitude Varies by Location
During the eclipse, the sun will be at a low angle in many parts of the path of totality.
- Iceland: The sun will be highest here, at around 25° above the horizon.
- Northern Spain: As you move west to east across northern Spain, the sun’s altitude will decrease, from approximately 12° in the far west to about 8° in places like Bilbao.
- Mallorca: Totality here will occur just before sunset, with the sun a mere 2.4° above the horizon.
This difference in altitude is crucial. A higher sun angle means you are less likely to have your view obstructed by distant clouds. Conversely, a very low sun means you must consider a much larger area for potential cloud cover
At what distance must a middle cloud (7 km height) be to cover the sun being at an altitude of 2.4°?
It is a simple trigonometric calculation, taking into consideration small corrections for atmospheric refraction at low sun heights and Earth’s curvature at high distances.
Both of these corrections are applied in the figure below, which represents the distance at which a cloud must be to cover the sun at different heights and at different altitude of the sun. The vertical axis represents the height with respect to the observer, so if you are observing from a 1500m high mountain you need to rescale the position of the clouds
A low sun angle, like the 2.4° in Mallorca, means a large, distant storm cloud could be a significant problem. A storm cloud as far as 200 km away could block your view. This is in stark contrast to the view in Iceland, where, with the sun at a high 24°, only clouds directly above or very close to your location could ruin the show.
By clicking on a location on our online map https://maps.besselianelements.com/map/TSE20260812/ , a red line will show the direction of the sun during totality, pinpointing 3 spots corresponding to the height limits of possible low, medium and high clouds.
So, when checking weather forecasts on sites like www.windy.com that reports the position of different types of clouds, you will have to make sure to look for clear skies not above your head but along the line of sight to the sun at different distances according for different cloud heights