The Loo is a strong, dusty, gusty, hot, and dry summer wind from the west that blows over North India and Pakistan's western Indo-Gangetic Plain. It is especially strong in May and June. Exposure to it often results in fatal heat strokes due to its extremely high temperatures (45 °C–50 °C or 115 °F–120 °F).
Because of the extremely low humidity and high temperatures, the Loo has a severe drying effect on vegetation, causing widespread browning in the areas affected during the months of May and June.
Origins of the Wind Loo
The Loo is thought to have originated in the large desert regions of the northwestern Indian subcontinent, specifically the Great Indian Desert, the Cholistan Desert, and the desert areas of Southern Balochistan.
The wind Loo comes to an end with the arrival of the Indian monsoon in late summer. Before the monsoon, there are brief but violent dust storms known as Kali Andhi (or Black Storm) in some parts of North India and Pakistan. The presence of monsoon clouds in any location is usually accompanied by cloudbursts, and the sudden transformation of the landscape from brown to green as a result of the ongoing deluge and the abrupt cessation of the Loo can appear "astonishing".
Water evaporates quickly during this season because the plains of North India and Pakistan are both extremely hot and extremely dry. Although this causes many ponds and lakes to dry out, the extreme dryness of the air can also be used to create evaporation-based cooling systems. Windows shielded with fragrant Khas (/ or vetiver) dry-grass fibre-screens that are kept damp with a simple water-pumping mechanism are quite effective as an inexpensive form of air conditioning and have been in common use throughout the plains of the northern Indian subcontinent for centuries.
Because evaporation occurs at such a rapid rate in extreme dryness, the cooling effect can be quite dramatic, resulting in homes with chilly interiors. However, because the water in the screens evaporates so quickly, it must be constantly replenished from raised tanks or with pumps (that can sometimes be driven by the Loo itself). Any water reservoir that is used must also be protected from the Loo and the sun, or it will quickly deplete.
Effects of Loo wind
During the summer months, many birds and animals are killed by the Loo, especially in deforested areas where the Loo blows unhindered and shelter is unavailable. Certain insect-borne diseases, such as malaria, have historically seen a drop during the Loo season, as insect populations plummet. Even before the 1897 discovery that mosquitoes transmitted malaria, officials in Asia noticed that the strong winds in Northernmost India's plains naturally kept the region relatively free of the disease. The loo is often referred to as an evil wind in traditional Indo-Pakistani culture because of its destructive and potentially lethal effects on trees, humans, and animals. For children and the sick, as well as pets, avoiding proximity to the toilet is highly advised. During the Loo-affected months, most people want to spend as much time indoors as possible in the afternoons. Heatstroke is generally referred to as loo lagna which translates to being afflicted by the loo. During the Loo season, sharbat is usually sold, since they are widely believed to have a cooling impact on the body and have some defence against Loo-caused heatstrokes. Rose sherbets, khus-khus, shahtoot, bel, and phalsa are among them.