arduous

He hasn't founded yet.

'We will not lose hope,' says Michael Mosley's wife
https://www.bbc.com/news/articles/c0ddpwwrp3no

Words
advocate
terrain sounds like train
sniffer - a sniffer dog
arduous[quote]why the missing presenter would try to make a long, potentially arduous journey in such heat[unquote]
Hay Festival

I want to listen to The One Show, but it's too gossipy.

On the coastal path near where Michael Mosley was last seen
https://www.bbc.com/news/videos/cv22dz0w7k2o
rugged coastline

The route Michael Mosley is thought to have taken
https://www.bbc.com/news/videos/c3gg78wn434o
unforgiving hillsides / unforgiving landscape
scouring all these rocky facings
working theories
we've seen drones up

it's exceedingly hot
it's sweltering
it's incredibly hot
it's unrelentingly hot

It's not mentioned in the article or footages, but I saw some articles which said it was 37.5 or 40 degrees. It's exceedingly hot, indeed.
He used an umbrella, but he might get heat stroke...