He is aiming to cycle from Land’s End to John o’Groats by New Year’s Day and could finish the trip earlier than expected.
David Hay set off on Christmas morning on the journey inspired by his late wife, Janie.
Janie died after battling against ovarian cancer in 2013 at the age of 39.
David wanted to make the trip at Christmas to reflect the difficulties families face losing their relatives to the disease at this time of year.
His efforts have already raised more than £20,000 for five different cancer charities, including Macmillan and Cancer Research UK.
The 38-year-old, living in Glasgow but originally from Conon Bridge, Highlands, hopes to reach John o’Groats by tomorrow.
David’s father, Ian Hay, 64, is immensely proud of his son’s efforts.
He said: “We are so proud of him and are just astonished at what he’s achieved.
“He only took up cycling a few years ago and he’s been planning this journey around a year now.
“There’s a possibility that he could actually finish the journey early.
“He’s due to finish up in Golspie, Highlands, tonight (Tue) but might go further depending on how well he does.
“After that, it’s only around another 60 miles to John o’Groats.”
Ian does not think that David will do any more charity trips like this one.
He added: “That will be him after this, this was his big event and I don’t think he’ll do anything else.
“David had a very hard time in the years before Janie died and that’s partly why he wanted to do something like this.
“He wanted the trip to be challenging. That’s why he decided to do it during the winter and set off on Christmas morning.
“He was expecting ice and snow but has been caught up in the flooding in the north of England.
“David has done amazingly well.”
Many people have followed David’s progress via a tracker on his website, and some have even helped him on different sections of the journey.
Ian said: “People have been great at helping him.
“The support he has had from everyone, even from complete strangers, has been great.
“Even in our local area, the support for him has been huge and it has left us feeling very humbled by it all.”
By the end of his trip, David will have cycled almost 900 miles and climbed more than 33,000ft.
Last night, the total amount of money he raised stood at £21,735.80.
Anyone who wishes to donate can do so by going to https://mydonate.bt.com/fundraisers/davesbigicicleride.