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The direction of wind flow around an atmospheric high-pressure area and a [[low-pressure area]], as seen from above, depends on the hemisphere. High-pressure systems rotate clockwise in the northern Hemisphere; low-pressure systems rotate clockwise in the southern hemisphere.
High pressure systems in the temperate latitudes generally bring warm weather in spring and summer, when the amount of heat received from the Sun during daytime exceeds what is lost at night, and cold weather in fall and winter when the amount of heat lost at night exceeds what is gained during daytime (with low pressure systems it is the reverse--lows in fall and winter bring warmer weather and cooler weather in spring and summer).
The latitudes of 30N and 30S, the so-called "horse latitudes", have semi-permanent high pressure around them known as the subtropical ridge, although their size and exact location varies with the seasons. On the West Coast of the United States, the subtropical ridge expands in spring and brings the region's characteristic rainless summer weather. As it shrinks in fall, the West Coast is subject to cold fronts from the Pacific which bring rain during the cool months. On the East Coast, it brings warm, humid air in late spring and throughout summer. In fall, as the subtropical ridge retreats, cold air from Canada takes over. In Europe, the effect is similar as the subtropical ridge brings the Mediterranean hot, dry summer weather and cool, wet winters. Europe north of the Pyrenees is at a higher latitude so the effect of the ridge is somewhat less significant and this region is mainly characterized by a cooler maritime climate. However, a particularly hot summer such as 2003 or 2019 which sees the subtropical ridge expand more than usual can bring heat waves as far north as Scandinavia—conversely, while Europe had record-breaking summer heat in 2003 due to a particularly strong subtropical ridge, its counterpart in North America was unusually weak and temperatures across the continent that spring and summer were wet and well below normal.<ref>{{cite web | url=https://earthobservatory.nasa.gov/images/3714/european-heat-wave | title=European Heat Wave | date=16 August 2003 }}</ref>
In the Southern Hemisphere the result is similar. Australia and the southern cone of South America get hot, dry summer weather from the subtropical ridge and cooler wetter winter weather as cold fronts from the southern oceans take over.<ref>{{cite web |title=A dry start to winter |url=http://www.bom.gov.au/climate/updates/articles/a025.shtml |website=boom.gov.au |publisher=Australian Government Bureau of Meteorology |access-date=19 October 2022 |archive-url=https://web.archive.org/web/20221012200923/http://www.bom.gov.au/climate/updates/articles/a025.shtml |archive-date=12 October 2022 |language=en-au |date=July 2017 |url-status=live}}</ref>
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On weather maps, these areas show converging winds ([[Contour line#Wind|isotachs]]), also known as [[Convergence (meteorology)|convergence]], near or above the level of non-divergence, which is near the 500 [[wikt:hectopascal|hPa]] pressure surface about midway up through the troposphere, and about half the atmospheric pressure at the surface.<ref name="Gloss3" /><ref name="Match" />
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==Typical conditions==
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