- Spring Weather mode will start to appear in late February and early March for parts of Europe and the United States. Polar Circulation is starting to power up, as the pressure and temperature in the polar Stratosphere are now dropping. The response is more southerly flow into the mid-latitudes. https://www.severe-weather.eu/weather-trends/polar-circulation-spring-weather-united-states-europe-fa/ 8 comments worldnews