Why UAE's heat and humidity persist: Insights into October's weather trends

Abu Dhabi: The heavy humidity felt across parts of the UAE on Tuesday morning fits a familiar seasonal pattern: temperatures begin to fall overnight, but moisture remains abundant in the air, bringing uncomfortable conditions and an increased chance of fog.

Moisture carried inland from the Arabian Gulf, combined with clear skies, light winds and falling overnight temperatures, creates the conditions for high humidity, according to the National Centre of Meteorology. As the air near the ground cools, it moves closer to saturation, increasing the likelihood of fog.

The pattern is expected during the transition from summer into autumn and towards winter. The NCM expects humidity to remain elevated during October, meaning cooler weather will not necessarily bring an immediate end to damp, sticky mornings.

North-westerly winds can carry moisture from the Gulf towards coastal and inland areas during the evening and night, the centre explained. When those winds weaken, moist air can remain close to the surface.

Clear skies then allow the ground to lose heat overnight, cooling the air directly above it. As the temperature falls towards the dew point, the temperature at which water vapour begins to condense, relative humidity rises.

That increase can happen even without more moisture entering the air. Relative humidity measures how close the air is to saturation at its current temperature, so a cooler morning can have a higher humidity reading than a hotter afternoon.

When saturation is reached, water vapour condenses into tiny suspended droplets, forming fog. The NCM identifies relative humidity approaching 90 to 100 per cent, sufficient moisture, calm conditions and falling surface temperatures among the main ingredients.

High humidity also makes warm weather feel more oppressive because sweat evaporates less readily, reducing the body’s ability to cool itself.

The atmospheric conditions above the surface can help prolong the moisture build-up. High pressure in the upper atmosphere limits rising air, while overnight cooling can produce a surface temperature inversion, with cooler air below a warmer layer.

This arrangement suppresses vertical mixing and helps keep moisture concentrated near the ground. It is associated with radiation fog, one of the most common types in the UAE.

Wind speed makes a difference. Although north-westerly winds can transport moisture inland, stronger winds can also disrupt fog formation by mixing the lower layers of air. Their effect depends on their strength and the moisture content of the air they bring.

For those wondering when conditions will improve, there are two timescales to consider.

Within a day, warming after sunrise can lower relative humidity and help disperse fog. An increase in wind can also break up the shallow layer of moist air. Neither process necessarily means the moisture has disappeared, and humid conditions can return overnight.

Over the coming weeks, the NCM’s October outlook indicates that humidity will remain high. It lists the month’s average maximum relative humidity at about 78 per cent, a climatic average rather than a ceiling on individual readings or a prediction for every location.

The immediate forecast also points to humid conditions on Tuesday night and Wednesday morning over some coastal and inland areas, with a chance of fog or mist.

Relief from the sticky conditions will depend largely on falling temperatures. Although humidity is expected to remain high through October, cooler weather should gradually make it feel less oppressive. High relative humidity can still occur on winter nights and mornings, when it can contribute to fog without producing the same discomfort associated with summer heat.

The NCM noted that fog occurs more frequently during December, January and February, which meansx that the end of hot weather does not mean an end to humid conditions.

October’s outlook also anticipates temperatures above the monthly average and rainfall slightly above average. The seasonal shift will be gradual, with warm days, humid nights and occasional fog continuing along the way.