Hi Gary! Some perennial seeds need a freeze-thaw cycle to break dormancy, but if you don't want to leave seed trays outdoors over winter you can chill seeds in the refrigerator (not the freezer) after sowing. Seeds that don't need chilling could be started now, but seedlings might not be big enough to plant in the garden before winter. I'm assuming that in your Zone you will get a good number of frosts and thaws which will tend to push newly planted perennials up out of the soil. As this is a problem for me I over-winter perennial seedlings in an unheated garage - they freeze solid occasionally, but stay in their pots - and transplant them outside in spring. Can you give us a list of the perennials that are you thinking of growing?
Cross-posted with Caroline. Great minds think alike!