Shanghai is baking under a relentless sun, and there is no respite on the way.

Yesterday the temperature hit 39.6 degrees Celsius, making it the equal hottest day in the city in 63 years, and the second highest since weather record-keeping began. The mercury reached the same level on July 25, 2003, and on July 6, 1944.

The latest heat wave has had a multi-tiered fallout, including:

- Record consumption figures in both water and power that pose a grave supply threat.

- A dramatic increase in emergency cases of heat-related ailments and distress.

- Warnings from the weather bureau about the dangers of overexposure to the heat.

After a hot and sticky night, yesterday's temperature had already eclipsed 35 degrees in the early part of the morning.

The meteorological authority issued a yellow warning on its Website about 9:40am, announcing another day of above 35 degrees.

Forecasters upgraded the warning level to orange, their second-highest alert, only an hour later as the mercury continued to climb towards 39 degrees.

It was 39.6 degrees about 2pm - not far shy of the 40.2 degrees, the city's hottest day on record that occurred on July 12, 1934.

The maximum temperature on Saturday was 39.1 degrees.

The city officially entered summer on May 13, the earliest the season has arrived in a decade. And there is no escape for residents and visitors. The forecast for the next five days is for minimum temperatures of 28 to 29 degrees, highs ranging between 35 and 39, and thunderstorms on Wednesday.

Forecasters estimate that the city will have 22 days when the temperature passes the 35-degree mark. If they are correct, 2007 will become the hottest summer on record.

The bureau has issued an "important warning" on its Website, suggesting that people cut down on time spent outdoors to avoid sun stroke, sun burn and other complications.

The Shanghai Center for Disease Control and Prevention was on the alert before the weekend, warning those at risk, such as children, the elderly, heart-disease patients and the overweight, to stay indoors.

From July 17 to 19 alone, the admissions to local hospitals had already risen by 19 percent from the same period last year. Center officials said there was a definite link between the patient intake and the heat.

The city is also creating records in the use of tap water and power.

Shen Yiyun, an official with the Shanghai Water Authority, said yesterday that the heat wave has caused an enormous strain on supply.

"Tap-water supply has been reaching our maximum capacity over the past couple of days, and creating records," Shen said.

The latest available figures for city tap-water use were released yesterday. On Friday, 10.15 million cubic meters were consumed, which set a daily-supply record. On Saturday, 6.87 million cubic meters of tap water was supplied just to the city's downtown area, another record.

The electricity-supply network is also under great stress. The latest power-supply peak, which also created a city record, occurred at 1:50pm on July 20 - an astounding 20.37 million kilowatts.

The power company has urged people to cut down on consumption to avoid electricity blackouts