An extreme heat warning was in place in Beijing on Tuesday as temperatures soared across northern China, after a swathe of the northern hemisphere baked under record highs.

China is the biggest emitter of the greenhouse gases that scientists say are driving climate change and longer, hotter heatwaves.

Authorities in Beijing issued an orange alert for extreme heat on Tuesday, the second-highest level in a four-tier system, warning that the mercury could climb as high as 37 degrees Celsius (98.6 degrees Fahrenheit) in some parts of the capital.

The municipal government urged residents to reduce time spent outdoors, drink plenty of water and monitor children, pregnant women and the elderly for signs of heatstroke.

High temperatures of up to 42C are forecast to persist across northern, northwestern and central areas, including Beijing, Tianjin, Hebei, Shaanxi, Hubei, Inner Mongolia and Xinjiang, until Friday, according to the national weather office.

But heavy downpours were expected further south, with up to 70 millimetres (2.8 inches) of rain threatening parts of Yunnan and Guizhou provinces on Tuesday and Wednesday, the weather office said.

Last month was the hottest May on record and was the 12th consecutive month of historic heat on Earth, the EU climate monitor announced last week.

Countries across the northern hemisphere have logged sweltering heatwaves as they move into the summer months.

India's top weather expert said Monday the country's current heatwave was the longest ever recorded, with parts of the nation -- itself a significant greenhouse gas emitter -- seeing temperatures above 45C since mid-May.

Parts of the western United States have also seen record heat for this time of year, while the island nation of Cyprus last week suspended outdoor work and food delivery services as the mercury hit 43C.