40F and moist part of the hours in a calendar day, as nights, is cold enough. If you were stratifying indoors, you would be using your refrigerator which is approx 40F, not freezing. With some seeds, the fluctuating temps between day and night can help to encourage germination.

I'd put them outside.

Martha

A friend of mine started Echinacea under her grow light last year with no cold stratification at all and had good germination from what I can remember. Don't think you will have any problems setting them outside now, even if you don't get much more cold weather. ;-)
CMK

I've started them inside with no pre treatment too and had good germination but seed was fresh. For most types echinacea, the general suggestion is a brief moist chill if reluctant to sprout. E. paradoxa and tennesseensis may do better if kept warm and moist 3-4 weeks, then chilled, then warm again.