You really should address that question to Rae
(should be some contact info at: http://runraerun.org/
I can tell you that she said, from Ohio (I think or somewhere around there) all the way to Colorado when she got up into the mountains, the temperature never was below 90. I ran with Rae two times last summer, once in July and again in August, through part of Nebraska and can confirm that was certainly the case then. If she encountered any such conditions maybe near the beginning of her run last April starting at Boston.
Also, Rae has worn shoes a couple of times, at least once when the road began getting too hot on a long day, and another time, I think on a gravel road.
But, I can also tell you that her technique could use some work, she pounds a bit harder than she needs to, and that would make gravel roads very difficult.
Since my two short runs with her in Nebraska, I've only been escorting her since Friday (yesterday), and the coldest it's been since then, was this morning at about 60F, about 65F when we finished a couple hours ago. Yesterday was warmer. Probably will be warmer tomorrow too, as we get closer to the beach where the climate is more moderate.