Milder temperatures forecast for the remainder of the week after a blistering Tuesday

Unlike the recent heatwaves Sydney has endured, the hot weather being experienced today is only expected to last for one day.

The Bureau of Meteorology has forecast a top temperature of 37 degrees for the Sydney area.

Tuesday’s heat is the a result of a surge of cold air in southeastern Australia which is pushing a mass of warm inland air into NSW ahead of the approaching front.

At 1pm on Tuesday Sydney was sitting on 35 degrees, which was 20 degrees warmer than Melbourne at the same time.

At Lucas Heights the mercury had reached 34.6 degrees by 2pm while at Sydney Airport it was 36 degrees at the same time.

Bankstown had record 35.4 degrees at 2pm.

Winds are NW 25 to 40 km/h tending Westerly in the late afternoon then becoming light in the evening.

Bureau of Meteorology forecaster Katarina Kovacevic said Sydneysiders the hot temperatures were only expected to last for one day unlike recent heatwaves.

"After midnight, we'll see a fresh and gusty southerly change move through the Sydney basin," Ms Kovacevic said.

"That will mean markedly cooler temperatures for Wednesday."

The remainder of the working week is looking much milder with forecast temperatures of 26 degrees through until Friday.

The NSW Rural Fire Service has declared a total fire ban across the state due to today's hot, dry and windy weather.

Today marks the first statewide total fire ban for 2019.

Conditions will be worst in the Hunter region, where the fire danger rating is extreme, while nine other regions across the state including the Greater Sydney region are expecting severe conditions.