Orange alerts, the second-highest level of China's three-tier warning system for high temperatures, have been issued for a number of regions as a heat wave continues in northern China, with parts of the northeast bracing for even higher temperatures in the days ahead, the China Meteorological Administration said.

Among those issuing orange alerts during the first heat wave of the year was Beijing, where temperatures hovered around 38 C on Sunday and Monday. According to the CMA's National Meteorological Center, the heat wave is likely to continue through Wednesday in the Beijing-Tianjin-Hebei region and other parts of northern China, with temperatures exceeding 40 C in some areas.

Parts of northeastern China, including Liaoning and Jilin provinces, will experience temperatures above 35 C over the next few days, according to weather.com.cn, a website affiliated with the CMA.

Although it is still early summer, these regions are experiencing a quick onset of high temperatures, so it will already feel like the "dog days "of summer, a reference to the season's hottest period, said Ye Menglong, an analyst at the website.

Over the next three or four days, high temperatures are forecast to persist in northern China and regions along the Yellow River, and parts of Hebei and Shandong provinces will experience the most intense heat, with temperatures reaching around 40 C.

On Sunday, high temperatures included 39.2 C in Tianjin, 38.3 C in Beijing and 36.8 C in Fuzhou, Fujian province — all marking the highest temperatures reached in those cities so far this year. In areas of the Xinjiang Uygur autonomous region and Hebei, temperatures soared above 40 C, according to weather.com.cn.

The heat has been especially harsh in Jinan, the capital of Shandong province. By the end of June, Jinan is expected to have experienced high temperatures — those reaching or exceeding 35 C — for 16 days during the month, compared with just 5.7 days during an average June, the website said.

Authorities are urging precautions, including reducing outdoor activities, staying hydrated and avoiding prolonged exposure to the sun. The Beijing city government reminded people to adjust their diets and take precautions when working outdoors in high temperatures.

During summer, temperatures inside closed vehicles can soar to 60 or 70 C, posing danger. In one recent incident, a car in Huzhou, Zhejiang province, caught fire after extreme heat inside the vehicle caused a cellphone to overheat, China Central Television reported on Sunday.

Beijing's education commission advised kindergartens and other schools to reduce outdoor sports classes and similar activities during high temperatures. Schools are also required to inspect air conditioning units in dormitories, ensure an adequate supply of water, and prevent food poisoning due to spoilage.