News Service from House Harris

NSW: Hot and dry, hot and humid weather comes to NSW

SYDNEY, Feb 7 AAP - As much of NSW broils in near record weekend temperatures, health authorities urge caution and common sense to avoid potentially lethal heatstroke.

They say it's essential to avoid unnecessary exertion, drink plenty of water while cutting down on caffeine and alcohol.

More than 1,000 Australian die each year from heat-related illnesses, NSW Health says.

The Bureau of Meteorology forecasts the mercury will soar past 40 degrees in many parts of the state and in Sydney's west on Saturday and Sunday.

It will be less punishing in coastal areas, with maximums ranging from the high-20s to the mid-30s.

Dr Jeremy McAnulty, public health physician with NSW Health, has warned that the elderly and children are particularly vulnerable.

"It is vital that people are responsible for their own safety and make an effort to check on family members, friends and neighbours at least twice a day," he said in a statement.

Sick people were more susceptible to heat-related illness and anyone braving the outdoors should try to monitor themselves and those around them.

"... anyone exposed to high temperatures in their homes, workplace or at an event such as a sports carnival or festival," Dr McAnulty said.

Symptoms of heat exhaustion include nausea, dizziness, loss of appetite, weakness, headaches, vomiting, not sweating and reduced urine output.

Anyone with those symptoms should contact a doctor or get to hospital as soon as possible.

Motorists have been reminded not to leave their children or pets in locked cars while the RSPCA has advised pet owners to regularly monitor their animals for heat stress.

Coastal sea breezes are expected to moderate temperatures in Sydney itself, says the Bureau of Meteorology (BoM).

But lower temperatures mean sticky conditions, with daytime humidity levels expected to surge from 20 per cent in Sydney's west to 50 per cent by late on Saturday and early Sunday.

For people on the coast, night-time humidity will soar to 80 per cent by the early hours of Sunday, with the mercury holding at 24 degrees.

"That's a pleasant daytime temperature but it's not a pleasant nighttime temperature," BoM senior forecaster Elly Spark told AAP.

"Certainly, early morning, when the temperature is around 24, it will be quite sticky."

Water temps along the coast are in the low 20s, Ms Spark said, which means winds across the water will keep coastal temperatures below the mid-30s.

"The good news is that we've got this strong sea breeze coming in along the coast in Sydney this afternoon," he said.

"But there's going to be a big difference between what's happening on the coast and what's happening in the western suburbs (and farther west) where 40-plus degrees should be quite easily achievable."

The mercury will range from the mid 30s to the mid 40s in western and far western NSW and in the Riverina.

Along the north and south coasts temperatures will range from the low-to-mid 30s until the change on Sunday evening.

But the change, when it arrives, will be bring widespread relief.

"It won't be like the last few fronts where it just brings a little relief to Sydney," Ms Spark said.

"The cold air is going to push a long way inland.

The heatwave will force Sydney trains to slow as a precaution against sagging power lines and buckling tracks.

CityRail has ordered drivers to slow services down by 10km/h, the standard protocol during hot weather.