A record number of rough sleepers were referred to a specialist helpline by members of the public as sub-zero temperatures gripped the country.
More than 3,600 alerts were sent to StreetLink, which connects the homeless to local services, between Monday and Tuesday morning - the highest total ever for a 24-hour period.
The app enables people to alert agencies if they fear for the safety of those on the streets.
More than 2,000 of the referrals concerned people in London, with director Matt Harrison saying the level of concern was "inspiring to see".
He said: "In 2017, alerts from the public enabled us to connect thousands of rough sleepers to accommodation and support services, and we hope that together we can help even more vulnerable people to get their lives back on track this year.
"This record number of referrals is inspiring to see, and is the first step people can take to ensure individuals sleeping rough receive the support they need to get into the warm and move away from homelessness for good."
StreetLink, which launched in 2012, is a website, app and phone line that connects rough sleepers in England and Wales with local charities, councils and support groups.
In the past seven days, almost 14,000 people have signed up to StreetLink as users and supporters of the service, it said.