The crowd was announced at 18,341 as the Rockies matched a team record for the coldest home start. A game against the Montreal Expos on April 12, 1997, was played in a similarly frigid conditions.
A pair of Mets-Rockies games in the previous three days were postponed because of heavy snow.
Garland (2-0) allowed two runs and six hits. He walked none and struck out four.
Troy Tulowitzki homered and hit a go-ahead single. Dexter Fowler and Josh Rutledge also hit home runs as the Rockies won their sixth straight home game.
Eric Young Jr. and Carlos Gonzalez added three hits apiece for Colorado.
Up 3-2 after Tulowitzki singled off Jonathon Niese (2-1) to drive in Gonzalez, the Rockies broke it open with a six-run seventh inning against three relievers.
Colorado got a two-run single from Wilin Rosario, a two-run double from Todd Helton and RBI singles from Chris Nelson and pinch-hitter Reid Brignac. In fact, Brignac batted in place of Jordan Pacheco, who began the inning as a pinch-hitter for Garland.
Helton's double was the 573rd of his career, moving him past Ivan Rodriguez for 20th on baseball's all-time list.
Fowler connected for his seventh homer and Tulowitzki for his fourth in the eighth off right-hander Jeremy Hefner, who took the mound in relief.
Niese gave up three runs on nine hits in six innings. The Rockies finished with 17 hits, doing most of their damage against the Mets' bullpen.
Rutledge snapped a 1-all tie in the fourth when he drove a changeup from Niese into the left-field bleachers for his second home run of the season.
New York evened the score at 2 on David Wright's second RBI single, a comebacker that glanced off Garland's glove in the sixth.
NOTES: After being snowed out Monday, the Rockies swept a doubleheader Tuesday from the Mets. A game Wednesday that was wiped out by another snowstorm will be made up at Coors Field on June 27 at 4:10 p.m. ... Rockies OF Michael Cuddyer was scratched from the lineup as a precaution because of a tender hamstring. ... Fowler was back in the starting lineup for the first time since fouling a ball off his foot Sunday at San Diego. ... Ike Davis' RBI single in the Mets' eighth inning snapped his string of 10 consecutive games without a run batted in, which had tied a career high. ... Mets RHP Matt Harvey (3-0), the scheduled starter for Friday night's game in New York against Washington and RHP Stephen Strasburg (1-2), traveled back home Thursday ahead of the team. ... RHP Jhoulys Chacin (2-0) is scheduled to pitch the Rockies' series opener Friday against Arizona and RHP Ian Kennedy (1-1).