There are large sections of the world which have extraordinarily mild
winders, some which have none to speak of.  There is lots of land out there
that grows edible food year 'round.

However it is almost certainly the case that going through winters and
drought seasons and such wherein nothing but meat was available would be
something humans have adapted to deal with.  It does remain the case that
to date, the only food that humans have been shown to be able to live on
exclusively for very long periods of time without any ill effects
whatsoever has been meat.  There is probably some significance to this.