At times it has been so hot in Gemma McMillan’s home at Ropes Crossing near Penrith that she has bundled up her little boy Oliver to sleep in the car for the airconditioning.

On those days she tends to keep Oliver inside during the day to shelter from the sun that beats into the shadeless garden of their rented home.

“Living with a three-year-old in a house with no aircon or ceiling fans is tough,” she says. “In the past, we’ve gone to stay with my ex-partner’s mum, who has an aircon, but now we’ve broken up and I worry about my son when it’s really hot.”

Ms McMillan is one of 1500 people who have responded to a survey by the non-profit group Sweltering Cities, which is campaigning for political leaders to recognise increasingly high suburban temperatures as a public health crisis.

According to the HeatWatch report it released with the Australia Institute on Thursday, Penrith could face nearly two months of extreme heat – days above 35 degrees – a year by the end of the century if carbon emissions remain high. Even by 2050, the number of extreme heat days could hit the one-month mark.

The report, based on Bureau of Meteorology and CSIRO weather data and United Nations emissions modelling, investigates projected temperature increases in 12 federal electorates across western Sydney.

“This is a political issue,” says Sweltering Cities co-ordinator Emma Bacon. In the midst of the Black Saturday bushfires, Penrith endured a day when the temperature hit 48.9 degrees and was for a time the hottest place on Earth. More than 92 per cent of respondents to the survey agreed that political parties should have specific policies on extreme heat.

Due to its location at the base of the Blue Mountains, western Sydney electorates do not enjoy the benefits of cooling coastal breezes, a situation exacerbated by growing population density and urban design.