I've passed these Lilies on the roadside for years.
They show up briefly for short time in Spring here in Florida. Along roadsides with wetlands abuting the road. I always intend to stop on the way back and yesterday
I finally did so.
It turns out these are native lilies and are named Atamasco rain-lily (Zephyranthes atamasca).
\They flower a few days after a rainfall and thus the rain lily.

If I'm right they are Simpson's rain-lily one of the two varieties.