You can see trends of atmospheric pressures change on your Watch complications.

You do not need an internet connection to use this application. You can use it in the mountains, forest, or on the sea where there is no GSM mobile coverage.

This app works best with with Apple Watch Series 3 (use build in barometric sensor) Watch Series 0, 1 or 2 do not has bulid in barometric sensor so this app requires iPhone (6 or later). Reading of barometric pressure is make every 1 hour.
Knowing the tendency of pressure (rise or fall), you can to some extent anticipate change in the weather.

A rapid fall of air pressure is a sign for bad weather.
A slow and constand increase is a sign for an improvement of the weather conditions, A rapid incease is a sign for a shorter period of better weather and a sign for strong winds.

Pressure changes also affect our health eg high atmospheric pressure increases blood pressure and its coagulation. Low atmospheric pressure can cause headaches or migraines, disturbed concentration and irritability so it is good to know how barometric pressure is changing.