During the boreal summer, fluctuations of the West Africa monsoon are known to produce significant changes of the regional atmospheric circulation which affects rainfall, moisture, temperature and wind, as far north as the central Sahara desert. Large shifts of the monsoon are partly connected to the anomalous warming of the sea surface in the Guinea Gulf near the equator, providing a connection between the Guinean coastal region and the Sahel through both the thermodynamics and the dynamics, i.e. through the combination of different mechanisms and processes like: evaporation, atmospheric moisture content and its convergence and thus anomalous latent heat, as well as land/sea temperature gradient, latitudinal shift of the inter-tropical convergence zone, modified flux convergence, anomalous rising/subsidence patterns. The phase of the inter-annual fluctuation changes seasonally. Climatologically, during summer, the rising branch of the Hadley circulation located over the Sahel can influence, through the dynamics, different regions further North, such as the Mediterranean region. An interannual climatological analysis suggests that the SST (mean and anomalies) in the Guinea Gulf, through their effect on the West Africa monsoon, influence the central-western Mediterranean summer, and specifically the temperature and precipitation, giving rise to anomalous summertime climate. A southward shift of the monsoon is related to cooler and wetter conditions over the central and western Mediterranean sea in mid-late summer. While, when the monsoon influence moves further North, the summer is hot and dry over the Mediterranean sea. Statistical analysis of climatological data over the Region, and of NCEP/NCAR reanalysis and regional numerical simulations prove how effective are the SST and SST Anomalies in the Gulf of Guinea in modifying the Mediterranean summer climate. Therefore, Mediterranean interannual variability in terms of Geopotential, Temperature, and Precipitation fields, as well as in terms of modified storm tracks, is shown to be associated to the variability of the SST and of the associated African monsoonal regime.