São Joaquim

City hall sign indicating an absolute (unofficial) minimum temperature of -14 °C (-6.8 °F)

Due the altitude above 3280 ft (1000 m) and a few degrees below the tropics, the climate of the city is highland subtropical (Koppen: Cfb) modified for precipitation sufficiently moist in every month, more abundant throughout the year (usually more distributed than Campos do Jordão), with cool summers and low temperatures in winter, but not so below freezing point. The average annual temperature is 11.4 °C to 14.3 °C. Since the maximum average does not exceed 20 °C. At the same time, the minimum averages are above 7 °C. The annual precipitation is high from 1450 mm to 1650 mm and about 135 rainy days.[10] Winter precipitations can occur at crucial times in the seasonbut tend not to be plentiful and cumulative, except in few occasions.[11] Together with Urupema, Urubici and Bom Jardim da Serra and São José dos Ausentes, São Joaquim is considered the coldest city in Brazil if the maximum average temperature and the number of cold hours are considered (loses to Urupema and Bom Jardim in absolute minimums).[12][13] During the winter months, frost is common - every month they are subject to the phenomenon, being more common from May to September (in years of La Niña from April to October), although strong masses of polar air may enter as early as April. Outside winter, spring and fall may receive frosts due to the prevailing cold and dry air.[14] Frost can occur even in midsummer[15] and are 40.8 days on average per year where the freezing of soil and plants occurs between the years of 1980 and 2003 registered by the meteorological station in the place.[14]

Occasionally, in the days of more intense cold, precipitations occur in the form of snow, being one of the few Brazilian cities that receives snow almost every year, a rare phenomenon in the average cities of the south of the country. However, it does not appear many times a year, with an average of 5 to 7 days (for being above 1200 m) in the region in normal winters, and is rarely intense (normally the temperature rises with when the precipitation ceases), since the latitude of the city is relatively low to provide more abundant and more frequent snowfall precipitations.[16][17][18] In 1990 there were 12 days of snow, one of the snowiest years of the century.[18][19] The snow was already registered from April to October,[18] with the earliest occurring on April 16 and 17, 1999 (was the first snowfall this month, the second was in 2016),[20] and the later on October 3 of the same year, in the Cruzeiro district (in the city on September 30, 1980).[21] August is the most snow-favoring month. Between 1999 and 2010 were 10 days.[22] In general from June to August it can snow.[23]

São Joaquim covered with snow in 1968, 11 years after the state's biggest blizzard

According to data from the National Institute of Meteorology (INMET), from 1961 to 1983, 1988 to 1989, 1992 to 1998 and from 2000 to 2017, the lowest temperature recorded in São Joaquim (conventional station) was -9 °C (15.8 °F) on July 14, 2000.[24] Since 1961 there have been 10 times where the minimum temperatures reached -7 °C (19.4 °F) or less. For the same period until October 10, 2018 were 435 times when the temperature was at -1 °C (30.2 °F) or less below zero at 57 years.[25] The highest reached 31.4 °C (88.5 °F) on December 20, 1971.[26] Temperature records above 30 °C (86 °F) also occurred on December 19, 1971 (31 °C or 87.8 °F), January 4, 1963 (30.6 °C or 87.1 °F), January 6, 1963 (30.4 °C or 86.7 °F), February 1973 (30.1 °C or 86.2 °F) and 17 December 1995 30 °C (86 °F).[26] All in just 4 occasions the temperature has surpassed 30 °C (86 °F) since 1961, which is rare for a city in the 28th parallel or even for elevation.[27] On July 13, 2000, the temperature did not exceed -2 °C (28.4 °F), which was the lowest recorded in the period.[26]

The largest accumulated precipitation in 24 hours was 124.2 mm (4.889 in) on July 6, 1983. Other large accumulations were 123.1 mm (4.846 in) on August 17, 1983, 123 mm (4.843 in) on July 4, 1993,112 mm (4.415 in) on October 1, 2001, 111.6 mm (4.394 in) on August 9, 2011, 111.4 mm (4.386 in) on September 19, 2015, 109.3 mm (4.303 in) on November 6, 1974, 108.8 mm (4.282 in on August 19, 1965, 107.5 mm(4.232 in) on September 28, 2009, 105.5 mm (4.154 in) on February 21, 1994, 101.7 mm (4.004 in) on May 28, 1992 and 101.4 mm (3.992 in) on February 22, 1961.[28] The month of greatest precipitation was July 1983, with 28.992 in (736.4 mm).[29] The lowest relative air humidity was on August 30, 1976 with 19.5%. With a value below 20% there was another occasion on June 12, 1996 with 19.75% relative humidity, which is confused with the driest season of the year.[30]

In a country without persistent freezing, except for sporadic frosts in the south, São Joaquim is one of the few Brazilian cities where you are likely to observe snow most years. For this reason, the city is a tourist attraction for Brazilians, the majority of whom will never see snow. Located in an elevated area, it is an urban area with the highest number of snowy days, despite its location in relation to other higher rural areas.[31] On July 20, 1957 the city suffered the second largest blizzard in the country, and the largest in Santa Catarina with 1.3 m of accumulated snow, which is uncommon for a mostly tropical country. The city was isolated for a week and received supplies by air.[32] It snowed for 7 uninterrupted hours, and continued sporadically in the days following, temporarily closing the highways.[33]

Studies show the increase of the precipitation frequency with the warm phase of the Pacific decadal oscillation (PDO) and its decrease during the El Niño and La Ninã episodes. The average is 2.7 days per year in São Joaquim (value close to that of Greenville in the South Carolina) with the majority coming from polar anticyclones with an extratropical cyclone.[34] The maximum gap in the monthly range of snowfall was between April and October, i.e. between autumn and the first weeks of spring, considering the years 1980 to 2013. In the same interval the year with the most frequency was in 1990, at the same time that there were years without any occurrence. In descending order July and August are the snowiest months, period most affected by cold air masses.[35] Between 1980 and 2010, the city had 103 cases of snow, if the distribution were even, this would mean that in each year there were at least 3 days with this type of precipitation. In 36% of the cases, there is a causal relationship with the arrival of cold waves.[36] A few years ago they never received snow like 1971, 1986 and 2005.[31] Although other sources consider that flakes fall in the last year quoted previously and mark 1991 with no snowy day.[36]