Olly Murs said he has had a "special weekend" after embarking on a hike in memory of Caroline Flack.
The singer was part of a group who were aiming to climb 24 peaks in 24 hours in a bid to raise awareness and funds for suicide prevention charity Samaritans.
Love Island presenter Flack took her own life at the age of 40, on February 15 2020.
On Sunday, Murs posted an update on their progress from the summit of a peak in the Lake District, where the challenge has been taking place.
He wrote: "New peak at the Lake District!
"This one had no name, so we called it the "Flack Peak" this was a Special weekend with Special people, doing something for a very Special person!
"Thanks for all the messages of support and the donations xx."
More than £20,000 has been raised by the challenge so far.
In a video, Murs said: "Thank you so much from the bottom of my heart, from all of us."
He added: "My legs are sore, I've got blisters, my knees are so tired.
"I'm exhausted but I'm doing this for Caz, we are doing this for the Samaritans."
Murs, who worked alongside Flack on The X Factor, was joined on the walk by her former personal trainer Bradley Simmonds, stylists Lou Teasdale and Nana Acheampong and close friend Mollie Grosberg.
Donations can be made to the fundraiser at justgiving.com/fundraising/climb4caroline.