Various factors impact the average state of the atmosphere at a particular location. For instance, midlatitudes will have a pronounced seasonal cycle in temperature whereas tropical regions show little variation in temperature over the year.[16] Another major control in climate is continentality: the distance to major water bodies such as oceans. Oceans act as a moderating factor, so that land close to it has typically has mild winters and moderate summers.[17] The atmosphere interacts with other spheres of the climate system, with winds generating ocean currents that transport heat around the globe.[18]