The weather is regarded as the observations that cover the state of the atmosphere. This includes precipitation, suspended particles, atmospheric obscurity, and weather events like lightning. Present weather is a description of the weather phenomena present at the time of observation. Past weather is used to describe significant weather effects during the previous hour.

Systems to measure present weather are part of most national meteorological networks and are also part of most airport meteorological systems.

Specialized manufacturers are: Envirotech Sensors Optical Scientific, Vaisala, ScTi, Impulsphysik, Belfort and Biral.

The optical distrometer manufactured by by PMTech, can also be used as a present weather sensor and visibility sensor.