These two western Sydney streets are only 1 kilometre apart, but when it comes to temperature there's a lot that separates them.

Last summer, Galloway Street in North Parramatta experienced five days of temperatures above 40 degrees.

People on Daking Street — which is a short walk north — sweated through 13 days above 40 degrees.

It's the hottest street in the City of Parramatta's municipality.

The reason? Trees.

Key points: Tree cover on the streets of Parramatta can mean a difference of 10C on a hot day

Tree cover on the streets of Parramatta can mean a difference of 10C on a hot day Western Sydney's growth means more exposed bitumen could warm the area

Western Sydney's growth means more exposed bitumen could warm the area The Parramatta Lord Mayor is committed to planting more trees to alleviate the heat

Temperatures are predicted to soar across Sydney's western suburbs today.

In Penrith the mercury is predicted to be 38 degrees, while Richmond is tipped to reach 37 degrees.

New research from Western Sydney University has revealed the temperatures at ground level could vary wildly — in some areas the difference was more than 10 degrees.

The studies, led by Dr Sebastian Pfautsch, mapped the heat at locations in Parramatta, Cumberland and Campbelltown last summer.

Tracking the microclimates of specific suburbs found they were exposed to more extreme heat than recorded by the Bureau of Meteorology.

On Galloway Street in North Parramatta, the tree canopies keep the street cooler than others nearby. ( ABC News: Mridula Amin )

About 30 per cent of Galloway Street is covered by trees.

Meanwhile, Daking Street's 10 per cent coverage means it is left baking in the sun.

Dr Pfautsch said tree canopies and reflective surfaces could help reduce the temperature at ground level by as much as 2 degrees on a sweltering summer day.

Despite short distances, the temperatures in each location could be wildly different depending on the day. ( ABC News )

The fact Sydney's western suburbs are a construction hot spot, where the population is expected to swell to 3.5 million by 2042, also does not help.

"The whole process of developing Western Sydney, and the new airport, all of that will contribute massively to heat in the area — because you're losing surfaces where water can penetrate, and you have more bitumen," Dr Pfautsch said.

'Absolute heat traps'

Christelle Dardagos, whose son goes to school on Daking Street, said the heat was not hard to notice.

"It's pretty hot, not a tree in sight," she said.

"But mainly it's the reflection from the concrete that kills you.

"In a sense it's good to develop the area, but sometimes you worry, when you go out further and see the new estates, they're getting worse and worse, they're so close together, there's no trees, the streets are tiny."

Dr Sebastian Pfautsch said the development of western Sydney means more exposed bitumen to absorb and emit heat. ( Supplied )

Dr Pfautsch said solar radiation hit open surfaces — like those on Daking Street — which then conserved it and emitted it long after the sun went down.

City of Parramatta Council Lord Mayor Bob Dwyer said his team was taking steps to combat the heat.

"This includes planting more trees, incorporating urban heat requirements in new developments, delivering heat mapping, trialling the use of new cool materials in urban spaces, and collaborating with key stakeholders to inform even further action," he said.

Nor is climate change helping — last summer was Australia's hottest on record.

Last month, the NSW Government announced a plan to plant 5 million trees in Greater Sydney by 2030, in a move that would increase the city's canopy from 16.8 per cent to 40 per cent.

Dr Pfautsch wants to see it become law.

"We should legislate two trees [have to be planted] in the front yard," he said.

"If we continue building like what we see now and what we've seen the last five years, these are absolute heat traps and we're locking ourselves in for the next decades."