Summer solstice on June 21 marks official start of summer

Dubai: As the summer solstice arrives on June 21, it marks the official start of summer and the longest day of the year. While this astronomical event signifies peak solar radiation, it doesn’t always correlate with an immediate surge in temperatures.

The term "solstice" originates from the Latin words "sol" (Sun) and "sistere" (to be still). It refers to the two times each year when the Earth's axis is most tilted either towards or away from the Sun. During the summer solstice, the hemisphere tilted closest to the Sun experiences its longest day, while the opposite hemisphere has its longest night. For the Northern Hemisphere, the summer solstice consistently occurs around June 21.

In the UAE, the summer solstice on June 21 signifies the point when the Sun's rays are directly overhead the Tropic of Cancer (23.37 degree North). This alignment results in the country experiencing its longest day of the year in terms of daylight hours.

While June 21 officially ushers in summer and marks the longest day, it doesn't necessarily trigger a sudden and drastic increase in temperatures. Although daily temperatures in June in the UAE typically range from 47 °C to 49 °C, occasionally reaching 50°C, the direct impact of the solstice on this specific day's temperature is not a sharp surge.

The National Centre of Meteorology (NCM) reports indicates that the mean temperatures across the UAE generally rise by approximately 2°C to 3°C in June compared to May. This increase is part of a broader seasonal warming trend rather than an abrupt change directly caused by the solstice itself. The longest day signifies the peak of solar radiation for the year, but it takes time for this increased solar energy to be absorbed and re-radiated by the Earth's surface and atmosphere, leading to a gradual rise in overall temperatures.

It is common for the UAE to experience high humidity levels during June, particularly in coastal areas. This humidity plays a significant role in how hot the temperature "feels," often making it seem much warmer than the actual thermometer reading. This phenomenon is known as the heat index.

The level of humidity is largely influenced by the direction of the air mass. If the air originates from the sea, it will carry more moisture, leading to higher humidity. Conversely, air masses from the southeast or southwest parts of the country tend to be drier and more arid.

When both the air temperature and relative humidity are very high, the body's ability to cool itself through sweat evaporation is hindered, making individuals feel considerably hotter than the actual ambient temperature. Therefore, even if the temperature doesn't immediately skyrocket on the solstice, the combination of high temperatures and increased humidity can create a sensation of intense heat.

The summer solstice signifies that the UAE will experience progressively longer daylight hours in the weeks following June 21 compared to May. This extended period of sunlight contributes to the overall summer warming as the days maximize the amount of solar radiation received.