I claim the ornamental design for a jumbo thermometer, as shown and described.
FIG. 1 is a front top perspective view of the new ornamental jumbo thermometer of the present invention;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of portions of the jumbo thermometer is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.