Alfalfa planting dates

So for our area Purdue recommends August 1st thru September 1st to plant alfalfa, usually for a fall seeding I like to have it done before the end of the third week of August, this year the first half of August was bone dry and I had nothing but powder to plant in, after the record breaking rains (over 13 inches over 3-4 days) I still have water standing on the one field and the other is way too sticky yet. 

So the question is this, how far past the cutoff date have you gone in your area and still had a viable stand? I planted like the 7th to 8th of September once as was waiting on rain, then for it to dry back out (kinda like this year) but we also had a fall where we were hoping for a killing frost as the soybeans were a real booger to cut as the stems were still greenish, killing frost came a month late that year. Still making that field btw, its 5 or 6 years old now.

Alfalfa planting dates