It is a winter flowering orchid with greenish sepals and blue or mauve petals with large, irregular, darker spots.

The lobe on the top of the anther has a brownish back and crowded yellow or orange, finger-like calli.

[2][3] Thelymitra hiemalis was first formally described in 1988 by David Jones and Mark Clements and the description was published in The Orchadian.

[5] The winter sun orchid grows in heath and is only known from a few records near Portland, Anglesea, Upper Beaconsfield and Blackburn.

[2][3] Thelymitra hiemalis is listed as "endangered" under the Victorian Flora and Fauna Guarantee Act 1988.