More than 100 extra paramedics will be on duty as the NSW government declares a state of emergency over bushfire risk and soaring temperatures.
NSW Ambulance chief executive Dominic Morgan said on Thursday the paramedic service expected to respond to "some quite remarkable conditions" over the next seven days.
There has already been a 10 per cent increase in calls for patients with respiratory conditions over the past week as bushfires cause smoke inundation.
"This is a group of people who really need to be very vigilant; it can be a life-threatening condition," Mr Morgan told reporters in Sydney.
"Just this morning I became aware of a three-year-old who had such a severe asthma attack that they were unable to speak."
He said anyone in a "vulnerable group" such as the elderly or very young needed a plan to cope with the heat.
Anyone responsible for an elderly person should make sure they're well hydrated.
"The effects of heat exhaustion and heatstroke can be a life-threatening medical condition," Mr Morgan said.
He said an additional 187 paramedics would be rostered on throughout Thursday.
The Australian Medical Association has recommended people keep hydrated, cool and out of the sun during high temperatures.
The Bureau of Meteorology expects most of inland NSW will see temperatures in the mid-40s on Thursday, while areas west of the Sydney CBD are expected to top 41C.
RFS crews remain on high alert as they battle bushfires across Australia. Source: AAP
"In extreme heat, it's easy to become dehydrated or for your body to overheat, and the risk is especially high for children, the elderly, people with chronic illness, people who work outdoors and pets," AMA president Tony Bartone said in a statement.
Signs of heat exhaustion include dizziness and confusion, headaches, appetite loss, excessive sweating, leg, stomach and arm cramps and thirst.
NSW Premier Gladys Berejiklian along with NSW Ambulance Chief Executive Dominic Morgan. Source: AAP
