and a bottom face each with a surface area equal to that of the central square extent of the top face of the transparent housing as such the block defines a pair of prism shaped compartments 24 within the transparent housing situated within the interior space of the transparent housing are rectangular reflective layers 26 which line a bottom and rear surface of each of the prism shaped compartments the bottom and rear surfaces are defined by a portion of the bottom face of the transparent housing and a side face of the block respectively finally a transparent thermochromatic material 28 is situated within the prism shaped compartments for changing a color of light reflected off of the reflective layers upon a surrounding temperature dropping below a predetermined amount of about 32 degrees as an option a light manipulating layer 30 may be situated between the beveled side extent of the top face of the transparent housing and the thermochromatic material for dispersing and or diffracting the reflected light in the preferred embodiment the marker is mounted in direct contact with a road for indicating a freezing condition which may result in ice thereon it should be noted that the marker may take the form of other various shapes and further be mounted above the ground or on a sign adjacent to a highway as to a further discussion of the manner of usage and operation of the present invention the same should be apparent from.