WXIA in Atlanta reports that he was heard saying "I'm exhausted", but continued working.
Carter, 92, was hospitalized for dehydration, but said he was "okay."He has always been active with the non-profit group, which builds affordable housing for low-income earners.
Carter was in the city for the 34th annual Jimmy and Rosalynn Carter Work Project building 25 new homes in the province as part of 150 being built across the country with Habitat for Humanity.
"President Carter has been working hard all week".
Firefighters and paramedics went to the Winnipeg sight, and brought Carter to a local hospital, according to Canadian media.
Carter was in the sun helping build some stairs when he became pale and said he needed a break.
Carter has always been involved with Habitat for Humanity's work and, along with his wife Rosalynn Carter, sponsors the annual Carter Work Project.
Carter, a Democrat who served in the White House from January 1977 to January 1981, received the Nobel Peace Prize in 2002 for his humanitarian work. "His secret security. hydrated him by giving him some water and some Gatorade", Fielding said.
In recent years, Carter battled a deadly form of melanoma, discovered during surgery to remove a mass on his liver. "I feel special gratitude to God for giving me a few more days".