hi P B Walker,

Old spokes are always a problem during cold conditions.

Older spokes tend to become less in strength with usage and the cold might increase the brittleness to aid the breaking up.

Perhaps a plastic wheel frame support instead of spokes might be more useful in the cold conditions(BTW in my city its 92f during day and 65-70f during nights and we call it winter :-)).

regards
srinipartha