Answer:

barometer

Answer	Crossword Clue
BAROMETER	Meteorology tool
BAROMETER	Tool for weather forecasters
BAROMETER	It works under pressure

BAROMETER	Meteorologist's device
BAROMETER	It goes up and down
BAROMETER	Falling .. (picnicker's woe)
BAROMETER	Indicator of impending change
BAROMETER	Any indicator of change.
BAROMETER	Weatherman's instrument.
BAROMETER	Weatherglass.
BAROMETER	Forecaster's aid.

BAROMETER	Italian city takes on a forecaster
BAROMETER	Torricelli's invention: 1643
BAROMETER	Change indicator
BAROMETER	Opinion poll, e.g.