Keep a check on the humidity
Weather stations, digital hygrometers, and integrated weather meters. No matter what you call them, these compact, sensitive and accurate little units take the place of an entire shelf full of classic meteorology instruments, and their easy to read digital displays make reading those measurements a snap.
Popular Brands of Sensors and Weather Stations include Kestrel and AccuRite.
Weather meters use various different instruments and sensors. A hygrometer is a kind of humidity sensor. There are several types, each measuring a different combination of temperature pressure, electrical charge or mass to arrive at a determination of the absolute and relative humidity of the air. Luckily, modern digital hygrometers do all the math for us.
An outdoor thermometer is a very familiar instrument. It senses heat, and tells us the temperature of the air. A different type of thermometer detects what is called the wet bulb temperature on some units. This is the temperature the air would be if it was cooled to the dew point, or 100% saturation. Another type is the psychrometer or wet-and-dry-bulb thermometer.
An anemometer measures wind speed. This is typically a series of cups mounted on radial arms, which the wind causes to rotate. A barometer measures the air pressure. Rapid changes in barometric pressure have been used to predict storms for centuries. There are also other readings that do not come from one specific instrument.
Delta T or other forms of T is a reading of how universal time differs from terrestrial time. It is a shorthand for how the earth's rotation changes over the course of the year, or over centuries.
Dew point is the temperature at which the air would become saturated, at its current water vapour load. This is typically measured with a wet bulb thermometer or calculated from the temperature and humidity readings given by other instruments.
Many units also record historical trends, local historical highs and lows for temperature, air pressure, wind speed and other readings, so unusual readings can be interpreted.