Which of the following is likely a sign that it will rain soon?
Rising temperatureNo. A warm air mass moving into your area might bring rain, but it also might bring sunny weather. Rising temperature by itself is not a good indicator of rain.
Decreasing humidityNo. The humidity at ground level does not play much of a role in the formation of rain in the clouds. Just before it rains, the precipitation could cause the humidity to increase, but it would not cause it to decrease.
Wind out of the westNo. Any weather front moving in from the west could cause winds, even if it was bringing clear, sunny weather.
Falling barometric pressureYes! Low pressure fronts are commonly associated with rain and storms, so falling barometric pressure is a good indicator that rain may be on the way.
Click to see which state standards this question tests, and which of my videos, experiments, and other resources support that topic.
SC.5.E.7.3 Recognize how air temperature, barometric pressure, humidity, wind speed and direction, and precipitation determine the weather in a particular place and time.
UT.4.II.3.a Identify and use the tools of a meteorologist (e.g., measure rainfall using rain gauge, measure air pressure using barometer, measure temperature using a thermometer).
3-ESS2-1 Represent data in tables and graphical displays to describe typical weather conditions expected during a particular season.
MS-ESS2-5 Collect data to provide evidence for how the motions and complex interactions of air masses results in changes in weather conditions.