China has issued its first national drought notice of the year as authorities in the Yangtze river valley battle forest fires and mobilize specialized teams to safeguard crops from scorching temperatures.

The nationwide "yellow alert" was declared late Thursday after provinces from Sichuan in the southwest to Shanghai in the Yangtze delta endured weeks of excessive heat, with government authorities constantly claiming global warming as the cause.

The alert falls two levels short of Beijing's most severe warning.

Poyang Lake in central China's Jiangxi province, one of the Yangtze's important flood basins, has dropped to a fourth of its normal size for this time of year, according to state news agency Xinhua.

CCTV, a Chinese state-owned broadcaster controlled by China's Communist Party, reported on Friday that 66 rivers spanning 34 counties in the Chongqing area's southern portion have dried up.

This year's rainfall in Chongqing is 60% below the seasonal average, and the soil in numerous areas is severely dehydrated, according to local government data cited by CCTV.

Thursday temperatures reached 45 degrees Celsius (113 degrees Fahrenheit) in the northern Chongqing region of Beibei, China's weather bureau said.

On Friday morning, six of the ten warmest areas in the country were in Chongqing, with Bishan district temperatures surpassing 39 degrees Celsius. It was already 37 degrees in Shanghai.

As mountain and forest fires raged in the Chongqing region, the region's infrastructure and emergency services were under growing strain, with firefighters on high alert. State-run media also reported an increase in heatstroke cases.

As a result of "severe safety hazards," the gas company in the district of Fuling informed customers on Friday that they would suspend service until further notice.

In addition, the Chongqing agricultural bureau has established specialist teams to protect susceptible crops and increase planting in advance of the autumn harvest in order to compensate for losses.

To prevent supplies from running out, the water resources ministry has directed drought-stricken agricultural regions to create rotas dictating who can access them at any given moment.

According to data released late Thursday by China's emergency ministry, excessive temperatures in July alone caused direct economic losses of 2.73 billion yuan ($400 million) and impacted 5.5 million people.

Meanwhile, China's National Meteorological Center (NMC) repeated its high-temperature red notice on Weibo on Friday, marking the 30th consecutive day it has issued alerts. Forecasters anticipated that the current heatwave would not begin to subside until August 26.