"[They're] approximately 120 steps, it gets the heart rate up for sure."
The team - including Harris, Kevin MacDonald, Lisa McCallum and her son Corey - have fundraised to make it to the States, with help from helloworld Travel and American Airlines.
The group have been training about 10 times a week, following a programme that included spin classes and stair climbing.
"During our progress we've been doing a lot of climbing at Kennedy Park stairs. We've been to the Sentinel [in Takapuna], we train at Wolfs Gym in West Auckland on the stairmasters, Trusts stadium, anywhere there's stairs [where] we can get out and have some fun and join in," Harris said.
Another motivation for taking part in the stair climbs for the firefighters is to improve their fitness levels.
Harris said the team have been challenging and pushing each other to improve.
"It keeps us healthy. It's all about the fitness in the fire station as a whole, we're always encouraging each other to be fitter, faster and better, help us do our job better."
The Henderson team will donate to the designated charity of the Friends and Firefighters in New York, with a donation also going to the Leukemia and Lymphoma Society.
Support from the public has also spurred the firefighters in their training, Harris said.
"There's good interaction with the public here, every time we're here it's so busy, everybody stops and has a chat to us, we're enjoying it all, it's been good."
To donate, visit facebook.com/hendersonsponsor.