5 hot and dry or humid air masses control intensity of heat in UAE from June to August

The summer season in the UAE and across the Arabian Peninsula is one of the hottest seasons, extending from early June to the end of August, according to Ibrahim Al Jarwan, Chairman of the Board of Directors of the "Emirates Astronomical Society" (EAS) and a member of the Arab Union for Astronomy and Space Sciences (AUASS).

Al Jarwan told Al Khaleej newspaper that the UAE's summer is affected by 5 hot and dry, or humid, air masses coming from different ranges and control the intensity of heat and humidity during the summer season.

The most prominent of these is the Indian Monsoon Low, the most significant summer influence in the region, Al Jarwan pointed out.

He added that the Monsoon forms over the Indian subcontinent, and when it intensifies, its influence extends towards the Arabian Gulf, pushing hot and sometimes dry winds, or very humid winds when they interact with the humidity of the Arabian Sea and the Gulf. It is considered the main reason for the peak heat in summer.

Also affecting the summer weather are the extensions of the subtropical high-pressure system, which is a high-pressure system extending over land within a zone called the subtropical high-pressure belt, latitude 20° to 35° North and South. It works to stabilize hot weather and prevent the formation of clouds and rain, in addition to the maritime tropical air mass, which comes from the Arabian Sea and the Arabian Gulf. Its peak is from the end of July and throughout August, and it is hot and humid, responsible for the increase in coastal humidity, and increases the sensation of heat.

Al Jarwan added that the hot and dry continental tropical air mass, which originates over deserts and plateaus, comes from the Arabian Desert to the west, or from southwestern Iran and Pakistan to the east.

Its peak is in July, appearing as dry, extremely hot heatwaves inland, causing temperatures to rise in inland areas and leading to dry heatwaves and hot, dry winds known as "Samoom," sometimes accompanied by dust. Also, trade winds are active over the Arabian Sea, which are regular seasonal winds blowing from high-pressure areas southeast of the Arabian Peninsula towards the Indian subcontinent.

These may extend north towards the Arabian Gulf and when they strengthen and turn into humid southeasterly winds, and their extension coincides with the activity of the Indian Monsoon Low in July and August, they transport large quantities of water vapor from the Arabian Sea, causing an increase in humidity in the UAE, especially the eastern coast.

They also help in the formation of cumulonimbus thunderclouds over the “Hajar” mountain range and surrounding areas. Low or stratiform clouds may also form over the eastern coastal areas, sometimes accompanied by drizzle, and fog may form at night and in the early morning in desert areas, especially during August and September.

June is characterised by having the longest daylight hours of the year, as the sun is apparently directly overhead the Tropic of Cancer on the 21st, which increases the number of sunshine hours, potentially exceeding 13 hours and 40 minutes, coinciding with the summer solstice on June 21. Then, daylight hours gradually begin to decrease, according to Al Jarwan.

Al Jarwan continued: Average maximum temperatures during June are between 39- 42°C and lowest are between 27- 31°C. During July, the highest are between 41-43°C and the lowest are between 30-33°C.

Al Jarwan added that some desert areas record higher temperatures than these averages, while coastal areas are more humid, and temperatures gradually increase, starting from June to peak in July and August.

Humidity significantly increases starting from August, especially in coastal cities, during the night and early morning, which makes the sensation of heat higher than actual averages and causes strenuous weather, especially when high humidity coincides with high temperatures, Al Jarwn stated.

He indicated that humidity levels during June reach highs of 75%-90% and lows of 35%-45%, and during July, highs are 80%-90% and lows are 40%-50%.