How to prevent tire weathering?

[Rod]

I had four of my tires recently develop weathering cracking along the sidewall and within the tread pattern. The tires are a few years old but have about 90% tread. Now they wont pass a safety inspection around here.... 4 of the 6 tires on my one ton did this in the last 5 weeks. I parked the truck just after Christmas and now my tires are cracking. I suppose I could have taken them off and stored them, but I never had an extra 6 duallie rims with tires that held air.
Anyway Ive heard a few wives tales about how to prevent this from happening but figured I'd ask here also. I think warranty is not an option as I cant find a bill of sale for the tires... Firestone Steeltex ATX times 4 and 2 Steeltex R4S were on my duallie.

Mind you we had minus 55 degree temperatures recently with the wind chill... so I'm looking for ideas on weathering prevention from extreme hot to extreme cold.

In Canada where I am we have different problems than other warmer areas... my wifes car had the front main seal crack due to the cold also...seen it pop rear seals out of trannies too due to cold. So retirement may be in Arizona..LOL.