KUALA LUMPUR: Several cities are seeing hotter days, with the Meteorological Department issuing a yellow-level heatwave alert for seven areas in the peninsula on Friday.
Health experts have advised people, schoolgoing students and examination candidates to exercise caution, especially when outdoors, as extreme heat events could trigger heat stress conditions, such as heatstroke.
According to the Meteorological Department's portal, up to 4.30pm on Friday, the yellow areas experiencing scorching heat were Chuping in Perlis, Kota Setar in Kedah, Kuala Kangsar in Perak, Sepang in Selangor, Alor Gajah in Melaka, and Tangkak and Batu Pahat in Johor.
Sabah and Sarawak recorded no heatwave, and the maximum daily temperatures in the two states and other states in the peninsula were less than 35°C.
A Level 1 or yellow-level alert denotes a daily maximum temperature of 35°C to 37°C for at least three consecutive days.
A Level 2 or orange-level alert indicates a heatwave, where a daily maximum temperature of between 38°C and 40°C is recorded, and a Level 3 or red-level alert refers to a hazardous situation where the maximum temperature is more than 40°C for at least three consecutive days.
Universiti Selangor visiting professor of Environmental Health Dr Jamal Hisham Hashim said that in a hot environment, people might experience heat stress and heat-related illness, which can be in the form of heat rash, heat cramp, heat syncope, heat exhaustion and heatstroke.
"Heatstroke can be life-threatening," he told the New Sunday Times.
He said the ones most at risk were those who stayed for too long under the hot sun, such as landscape and construction workers, and those who commuted in non-air-conditioned transportation to work or schools, as well as those who did not hydrate themselves well by drinking water.
"Our study in 2016 showed that hydration is the best way to avoid heat-related illnesses, and drinking plain water is better than sweetened drinks.
"Hydrate yourself with plain water, eight to 10 glasses per day.
"Stay out of the hot sun and stay in the shade if you have to be outside for a long time.
"Wear light breathable clothing made of light cotton.
"If you have to exercise outside, do it early in the morning or late afternoon. Do not overwork yourself and always take drinking water with you.
"Elderly people should avoid strenuous activities at the moment.
"They are at the highest risk as their body thermoregulation is not as efficient as younger people, and they do not feel thirsty even when they are dehydrated."
Jamal advised schoolgoing children and examination candidates to take precautions.
However, he said, they did not need to worry about staying indoors for too long as school buildings in Malaysia were naturally ventilated, thus increasing fresh airflow.
"Our studies on schools in Malaysia showed that our classrooms are well ventilated and should not lead to excessive indoor temperatures."
A 2019 study titled "Thirst as the threshold symptom to prevent worsening heat-related illness", published in the Medical Journal of Malaysia, noted that common symptoms of heat-related illnesses were fatigue, cramps, nausea, dizziness, thirst, vomiting, confusion, muscle weakness, heat sensations on the head or neck, chills and lightheadedness.
Malaysian Public Health Physicians Association president Datuk Dr Zainal Ariffin Omar said people should stay in the shade, avoid direct sunlight and outdoor activities, drink a lot of water and eat more fruits.
"Extreme heat can cause people to have a headache, feel hot and uncomfortable, and get tired easily.
"Heat can trigger asthmatic symptoms because high temperatures and humidity cause air to not move, trapping pollutants that can irritate the airways," he added.
The Meteorological Department had, on Wednesday, said on Twitter that the areas most affected by the heatwave were Perlis, Kedah, Penang, northern Perak, northern Terengganu, and the inner regions of Pahang and Kelantan.
It said heatwaves, which generally occur during the last phase of the northeast monsoon until the start of the monsoon transition phase (February to mid-April), could trigger air pollution, drought, forest fires, and reduction in water levels at dams.
The department, however, did not expect unusually hot weather conditions to occur this year.
It advised everyone to drink enough water, reduce outdoor activities, avoid open burning, be savvy on water usage and store enough water, and not pollute any water source.
Up to 5pm yesterday, the Air Pollutant Index (API) in most areas in the peninsula recorded moderate air quality, with Rompin district in Pahang logging the highest reading of 92. Sabah and Sarawak had good APIs.
API readings of between 0 and 50 denote good air quality; 51 and 100, moderate; 101 and 200, unhealthy; 201 and 300 (very unhealthy); and over 300, hazardous.
The World Health Organisation had, in a 2018 report, said population exposure to heat was increasing due to climate change, and this trend would continue.
Globally, it said extreme temperature events were observed to be increasing in frequency, duration, and magnitude. Between 2000 and 2016, the number of people exposed to heatwaves increased by around 125 million.