AHS says it's based on temps between July, 1986 and March 2002. That should have picked up our -25 in 1990. Margaret L >Egad! They've moved me to zone 6! They used to have me in zone 5 and I've >always had to move down to zone 4 when buying plants to get them to survive. >Granted, we haven't had a zone 4 winter for several years and this past >winter our low was the lowest it has been since this drought started, only >down to -11. I wonder if they have based this map only on the past 4 or 5 >year's weather? > >Terry