Formation of very high cirrostratus or cirrus fibratus clouds at the very top of the troposphere with estimated altitudes of between 10.6km and 12.1km making them the possible highest clouds that could be observed over the Maltese Islands apart from polar stratospheric clouds such as notilucent clouds which were never observed locally thus far. In fact, these very high and thin clouds were indistinguishable during the day with their presence only being noticed around sunset when the Earth’s surface was under the shadow of the sun but the sky above still illuminated. In fact, these were unobservable in the satellite image. The first thumbnail is another view of the same cloud. Notice small undulatus features in the background on the bottom right hand side of the first thumbnail photo. The second thumbnail is the weather sounding that illustrates the atmospheric profile as explained. The weather situation was a slowly building high pressure system over the Mediterranean which would later yield to the first heat spell of the Summer.