Thermal rhymes with:
geothermal, hydrothermal, isothermal, bermel, dermal, endodermal, epidermal, geothermal, hydrothermal, isothermal, kurmel, mesodermal, turmel
Thermal sounds like:
terminal, terminally, thornell, thornhill, thornley, tramel, tramell, tramiel, trammel, trammell, tremel, treml, tremmel, triennial, trunnell, turmel, turmoil, turnley