The man, in his 60s, fell ill on Thursday morning (March 1) in Cheapside next to the Flag Market.
He had been referred to the Foxton Centre as part of their emergency Winterwatch scheme, which offers rough sleepers a place to sleep during subzero weather.
The man, who has not been named, left the centre in Knowsley Street at 8am on Thursday morning and was taken ill around 15 minutes later.
Joe McAteer, a Big Issue seller, was walking across the Flag Market from his home when he spotted the man in a doorway of the Turtle Bay restaurant and a neighbouring property, opposite the Flag Market.
He rushed back to his flat to get a blanket to cover the man up in the freezing temperatures.
Joe, 60, recalls: “The woman was giving him CPR and I held her phone for her so she could get instructions.
“He didn’t seem to be responding. You just go into autopilot trying to help.
“I didn’t know who the woman was but she did really well – when the paramedics arrived they took over and she said she had to go to work.
“After I finished my shift I went to the Foxton Centre to see how he was doing but they told me he had died.
“It’s thought he suffered a heart attack. I noticed he had an injury on his head and a bit of blood from hitting his head.
“I have heard that he was taken to the Foxton Centre by his neighbour the night before after being evicted from his property. It is very very sad.”
It's not known if the death if directly linked to the plunging temperatures but bosses at the centre said the tragedy highlights the need to look after the most vulnerable in society during the cold snap, which has seen temperatures fall to as low as -10C.
Foxton Centre CEO, Jeff Marsh, said: "This death has focused people's attention. The cold weather is horrible."
The centre itself was full to the brim on Thursday night, with 25 people staying in it, a further five in the community kitchen at Mill Bank Court and another five in other accommodation found by Foxton volunteers.
A spokesman for the Foxton Centre the man left the centre after having a shower and receiving a change of clothes.
"We understand he was taken ill about 15 minutes later in the city centre and died very shortly afterwards," the spokesman said. "This is a tragic event for all concerned and highlights the needs for continued work with the homeless and vulnerable in our community.
"There has been some very inaccurate reporting about these events which aren’t helpful and potentially very distressing to his family and friends.
"We will be pressing local agencies to look at this case in detail and see if there are lessons that we can learn from it."
The Foxton Centre said the man arrived at their premises on Tuesday on their emergency Winterwatch scheme, which offers rough sleepers a warn indoor place to sleep when temperatures are predicted to fall below zero for the night. The centre doesn't usually accommodate for overnight stays.
National guidelines state that local authorities must provide emergency accommodation if temperatures fall below freezing for three consecutive nights.
It comes as Lancashire is in the grip of one of the coldest periods in recent memories.
City ward Coun Drew Gale said: "I am devastated but not surprised. I whole heatedly believe such things are a result of government cuts.
"This is 2018 and people are dying because they are homeless. It should not be the case in a country with the sixth biggest economy in the word."
The incident took place as Preston and wider Lancashire suffers from extremely low overnight temperatures of minus four, with a yellow weather warning currently in place until Saturday evening.
Lancashire Police said: "We were called at 8:49am on Thursday, March 1, to reports that a man had been taken ill on Cheapside in Preston.
"The Ambulance Service attended, and the man, in his 60s, was taken to Royal Preston Hospital. Sadly, he was later pronounced dead.
"His death is not being treated as suspicious and a file has been passed to the coroner."
Foxton Centre CEO, Jeff Marsh, has commended the Preston community for their selfless work to help the most vulnerable in the city as the 'Beast from the East' and Storm Emma hit the red rose county.
Marsh said: "There's been a really good community effort in Preston. We have been overrun with donations this week.
"We have had no end of food donations for vulnerable people's free breakfasts, our kitchen is run by volunteers. It allows us to do things we couldn't do otherwise."
Jeff is also calling for the community to keep up the fight against homelessness when temperatures aren't as cold as they are now.
He said: "Next week it might be a bit warmer but we need to keep the attention on helping vulnerable people.
"We need long term solutions for people and that's why we are really excited by the Housing First scheme we are a part of."
The Foxton Centre currently has 22 people in its Housing First scheme, which looks to place people in shared accommodation before rooting out the cause of any problems they may have.
Jeff said: "We have 22 people - hopefully 24 by the end of today (Friday, February 2). It's shared accommodation taking people directly off the street.
"We get people into accommodation and then put in the support around issues that they may have.
"This week I was at a conference about the model with Sajid Javid MP, Secretary of State for Communities and Local Government.
"He wants to commit to ending homelessness. We need him to back up what he has said now."
How can you help?
There are a variety of organisations in Preston that do their bit to help the most vulnerable.
As well as the Foxton Centre, Emmaus in Ribbleton Lane and The Salvation Army in Harrington Street off support for those without a home.
The Salvation Army offer emergency accommodation in its lifehouses on a night-by-night basis to people who have nowhere else to stay.
A spokesman said: “The accommodation is basic but safe and secure and the staff on duty are available to support the individual through the night.
During periods of extreme weather, our lifehouses and churches make use of all available space in order to protect people from the cold.
“People are at their most vulnerable when the temperature drops, and many people sleeping rough will drink alcohol or take substances to help them get off to sleep in the cold.
“This has many ramifications for their body and the body’s ability to regulate their temperature. People are at severe risk of hypothermia, and it is our responsibility to ensure that we do what we can to prevent loss of life.”
A dedicated mobile app has been set up to report rough sleepers rough sleepers that you believe are vulnerable or in need or any help.
The app – StreetLink – lets you send details of rough sleepers to the relevant bodies to help them.
A spokesman for StreetLink said: “If you are concerned about someone sleeping rough in England or Wales, you can use this website to send an alert to StreetLink.
“The details you provide are sent to the local authority or outreach service for the area in which you have seen the person, to help them find the individual and connect them to support.”
StreetLink is available on both Apple and Android, as well as at www.streetlink.org.uk.