Why UAE weather brings dense morning fog and humidity as the long summer ends?
End of summer changes the UAE's local weather pattern
Dubai: As the UAE shifts away from the blistering heat of summer toward the cooler season, residents are experiencing the familiar blanket of thick, swirling fog, particularly in the early morning hours, often from 2 am to 9 am. Despite the summer officially ending, many wonder why the humidity and low visibility persist.
The appearance of fog during these months is a tell-tale sign of the weather transition, marking the gradual winding down of summer heat until the true winter weather arrives in December. This phenomenon, however, can be fully explained by the science of how air, temperature, and moisture interact in a coastal desert environment like the UAE.
The science behind the October fog
In essence, the September and October fog is a direct result of the clash between hot and cold air masses, particularly near the coast.
Sea breeze vs desert heat: As the weather cools, the air blowing from the Arabian Sea toward the land is noticeably cooler. Simultaneously, the desert sands, having absorbed intense heat throughout the day, release this hot air into the atmosphere overnight.
The mixing: When this warmer, rising desert air meets the cooler, sea-driven breeze, the moisture in the air rapidly precipitates. This process is similar to the 'misty eyeglasses phenomenon' you experience when stepping out of an air-conditioned space: the humidity in the warmer air instantly condenses upon contact with a colder surface.
High humidity and visibility: During this transitional period, especially in the early morning, humidity levels can soar as high as 90 per cent. When this high moisture content mixes with the fine sand and silica particles suspended in the air (carried by the breeze), the resulting mist is converted into the long-lingering, thick fog we see.
The fog often remains dense until the sun’s rays become intense enough, typically after 8 am, to warm the atmosphere and dissipate the moisture, clearing the roads for the day's traffic.
Thermal radiation and inland fog
Official reports also attribute the early onset of fog, sometimes beginning as early as September, to a process called 'thermal radiation.'
This is usually triggered by the Arabian Sea’s surface cooling down overnight. As the sea surface cools, it reduces the air's ability to hold moisture, leading to condensation that forms low cloud or fog over the coastal areas.
Furthermore, fog formation is not exclusive to the coast. In the country’s interiors, lower temperatures on the land during the late night and early morning hours cause inland fog to form. This type of fog can often be denser and may take even longer to lift as the land heats up more slowly than the coastal areas.
While foggy conditions can start early, the absolute foggiest days in the UAE generally occur from mid-December until the end of March. Until then, be prepared for low visibility on your morning commute as the climate completes its transition.
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