Jamie will be running across Canada during part of their winter, so will encounter Arctic temperatures he has never experienced before.
We took him to Gloucerstershire University's Sport & Exercise Laboratory where they have a chamber in which the temperature can be lowered to minus 20C.
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Another cloudy day but staying dry and bright with the odd sunny spells.
It's been a mostly sunny day but some patchy light rain is coming in from the west.
After a fairly sunny day the dry weather will mostly continue into this evening.