It is native to the southwestern United States and northern Mexico.

[2][3] Fimbristylis thermalis grows in alkaline mud and sand, especially around hot springs and mineral-rich seeps.

This is a thick-stemmed sedge which grows singly or in clumps and reaches maximum heights over a meter.

At the top of the stem is an inflorescence of ovate, pointed spikelets, each on a long peduncle.

The fruit is a shiny brown achene one to two millimeters long.