The Azores High (also known as the Azores anticyclone) is a semi-permanent anticyclonic region with relatively consistent high pressure and subsiding air over the Atlantic Ocean at around 30°N latitude in winter (i.e. south of the Azores). The Azores High is part of a belt of subtropical anticyclones on the northern hemisphere and an important so called 'centre of action' in the global climate system. (like its 'sisters' the Bermuda High and California high)
Movement of the system poleward in summer has a major impact upon the climate of Europe. In summer the pressure centre shifts towards 35°N across the Iberian peninsula and a ridge might build across France, northern Germany and even the south-eastern UK. This is when the typical mid- to late summer heatwaves arrive, with very hot temperatures and persistent dry weather. Temperatures will easily climb into the 30ies °C (90ies degF).
In both winter and summer the central pressure lies around 1024 mbar (hPa), but conditions are more variable in winter. The aridity of the Sahara Desert and the adjacent Mediterranean region is due to the subsidence of air in this high-pressure system.