This occurred as a line of bad weather in association with an unusually late mid-latitude cyclone or low pressure system (not the typical Spring heat lows) that developed over North Africa moved northeastwards passing over the Maltese Islands as depicted by the SLP chart on the fourth thumbnail. This chart is in line with the clouds over the visible satellite and the rain radar imagery on the fifth and sixth thumbnails respectively. The unstable airmass having originated from a much warmer area and passing over a very cool sea as depicted by ‘Il-Kaptan’ app, the pre-cold frontal airmass following this line of bad weather had cooled significantly inhibiting thunderstorm development at low-levels. During the late afternoon, fog enveloped the higher elevations of Malta as explained in the cloud post here ‘Frontal Zone‘ which was a very rare weather event for late May in Malta. Brief situation: A wintry low pressure system due to a strong jet stream forming over hot Africa and moving towards the cooler Central Mediterranean leading to a general stabilization and cooling of the airmass unlike in Winter when the warmer sea gives rise to instability hence the formation of low-based cumuliform clouds with sometimes heavy thunderstorms.