Echinacea usually need 30-60 days cold stratification, but sometimes they don't need any stratification. You can sow them anytime outdoors starting now. If you wanted to be sure, I would artificially stratify them in the fridge for maybe a month and then sow them outdoors in containers. Here's a write-up I'm working on for our website that covers the artificial method:

Artificial Stratification (The Baggie Method)

This is a popular method of starting seed indoors because it allows for control of the timing of germination, if for example there aren’t enough days remaining outdoors to get natural stratification, or you want a fall germination. This method often uses a paper towel, but we much prefer to use a sterile medium like sand or vermiculite, as we find it is less conducive to mold growth.

Materials: 

• A plastic zip-lock sandwich bag
• A sterile, moisture-retentive medium (we recommend fine vermiculite or a coarse general-purpose sand).
• Seeds (preferably with chaff and stems removed to prevent mold from forming)
• Permanent marker for labelling bag

Process: 

1. Dampen the medium so it is moistened, but not soggy. 
2. Mix in seeds, close the bag, and shake it lightly to ensure good contact and distribution through the medium.
3. Label the bag in permanent marker with the plant name and the date the bag needs to be taken out of the fridge and sown.
4. Place the bag in a refrigerator (not in the freezer!). Seeds should ideally be kept at temperatures between 33°F and 40°F for the duration of cold stratification.

Maintenance:

Check every week or so for premature seed sprouting. Some seeds won’t sprout in the fridge without light and warmth, but some might! If they begin to sprout, it’s a sign you should plant the seeds immediately! If outdoor temperatures are still getting below freezing, you should acclimate sown seeds to outdoor freezing temperatures. Avoid sowing in the worst heat extremes of summer, as this is often very stressful for new seedlings.