The ornamental design for a thermometercover, as shown and described.
FIG. 1 is a front perspective view of an embodiment of the present invention;
FIG. 2 is a front view of an embodiment of the present invention;
FIG. 3 is a rear view of an embodiment of the present invention;
FIG. 4 is a side view of an embodiment of the present invention;
FIG. 5 is a side view of an embodiment of the present invention;
FIG. 6 is a bottom view of an embodiment of the present invention; and,
FIG. 7 is a top view of an embodiment of the present invention.
The broken line showing of structural features is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.