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The Pampas (from Quechua pampa, meaning "plain") are fertile South American lowlands, covering more than 750,000 km2 (289,577 sq mi), that include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos and Córdoba, Chubut, most of Uruguay, and the southernmost Brazilian State, Rio Grande do Sul. These vast plains are a natural region only interrupted by the low Ventana and Tandil hills near Bahía Blanca and Tandil (Argentina), with a height of 1,300 m (4,265 ft) and 500 m (1,640 ft) respectively.
The climate is mild, with precipitation of 600 mm (23.6 in) to 1,200 mm (47.2 in), more or less evenly distributed through the year, making the soils appropriate for agriculture. This area is also one of the distinct physiography provinces of the larger Paraná-Paraguay Plain division. These plains contain unique wildlife because of the different terrains around it. Some of this wildlife includes the rhea, the pampas deer, several species of armadillos, the pampas fox, the White-eared opossum, the Elegant Crested Tinamou, and several other species.
The climate of the Pampas is generally temperate, gradually giving way to a more subtropical climate in the north, and to an arid climate on the west and the south. Summer temperatures are more uniform than winter temperatures, ranging from 20 °C (68 °F) to 32 °C (90 °F) in the north, 17 °C (63 °F) to 30 °C (86 °F) in most of the ares, and from 15 °C (59 °F) to 27 °C (81 °F) along the Atlantic coast. Extremely hot days might reach over 40 °C (104 °F).
Fall arrives gradually in March, and peaks in April and May. In April, highs will range from 20 to 25 °C (68 to 77 °F) and lows from 9 to 13 °C (48 to 55 °F). The first frosts arrive in mid-April in the south, and in late May or early June in the north.
Winters are generally mild, although cold waves do occur. Normal temperatures range from 12 to 19 °C (54 to 66 °F) during the day, and from 1 to 6 °C (34 to 43 °F) at night. With strong northerly winds, days of over 25 °C (77 °F) can be recorded almost everywhere, whereas during cold waves, high temperatures can be only 6°C (43F). Frost occurs everywhere in the Pampas, although it is much more frequent in the southwest, and less so around the Parana and Uruguay rivers. Temperatures under −5 °C (23 °F) can occur everywhere, whereas values of −10 °C (14 °F) or lower are confined to the south and west. Snow never falls in the northernmost third, and is rare and light elsewhere, except for exceptional events where depths have reached 30 cm (12 inches).
Springs are very variable, it is warmer than fall in most areas (especially in the west) but significantly colder along the Atlantic. Violent storms are more common, as well as wide temperature variations: days of 35 °C (95 °F) can give way to nights of under 5 °C (41 °F) or even frost, all within only a few days.
Precipitation ranges from 1,200 millimetres (47 in) in the northeast, to about 500 millimetres (20 in) in the southern and western edges. In the west, it is highly seasonal, with some places recording averages of 120 millimetres (4.7 in) monthly in the summer, and only 20 millimetres (0.8 in) monthly in the winter. The eastern areas have small peaks in the fall and in the spring, with relatively rainy summers and winters that are only slightly drier. However, where summer rain falls as short, heavy storms, winter rain falls mostly as cold drizzle, so that the amount of rainy days is fairly constant. Violent thunderstorms are common in the spring and summer
Frequent wildfires ensure that only small plants such as grasses flourish, and trees are rare. The dominant vegetation types are grassy prairie and grass steppe in which numerous species of the grass genus Stipa are particularly conspicuous. "Pampas Grass" (Cortaderia selloana) is an iconic species of the Pampas. Vegetation typically includes perennial grasses and herbs. Different strata of grasses occur because of gradients of water availability.
The World Wildlife Fund divides the Pampas into three distinct ecoregions. The Uruguayan Savanna lies east of the Uruguay River, and includes all of Uruguay and the southern portion of Brazil's state of Rio Grande do Sul. The Humid Pampas include eastern Buenos Aires Province, and southern Entre Ríos Province. The Semi-arid Pampas includes western Buenos Aires Province and adjacent portions of Santa Fe, Córdoba, and La Pampa provinces. The Pampas are bounded by the drier Argentine espinal grasslands, which form a semicircle around the north, east, and south of the Humid Pampas.
Winters are cool to mild and summers are very warm and humid. Rainfall is fairly uniform throughout the year but is a little heavier during the summer. Annual rainfall is heaviest near the coast and decreases gradually further inland. Rain during the late spring and summer usually arrives in the form of brief heavy showers and thunderstorms. More general rainfall occurs the remainder of the year as cold fronts and storm systems move through. Although cold spells during the winter often send nighttime temperatures below freezing, snow is quite rare. In most winters, a few light snowfalls occur over inland areas.
Central Argentina boasts a successful agricultural business, with crops grown on the Pampas south and west of Buenos Aires. Much of the area is also used for cattle and more recently to grow vineyards in the Buenos Aires wine region. These farming regions are particularly susceptible to flooding during heavy rainfall.
See also 
- Dry Pampa
- Federal University of Pampa
- Humid Pampa
- Médanos wines
- Médanos (dunes)
- Pampas Republic
- Rio Grande do Sul
- Encyclopaedia Britannica
- The Pampas
- Climate Impacts
- Centres of Plant Diversity
- Climate Guide to South America
- "Humid Pampas". Terrestrial Ecoregions. World Wildlife Fund.
- "Semi-arid Pampas". Terrestrial Ecoregions. World Wildlife Fund.