A polar air mass moved across southern Brazil in mid-June, bringing a sharp drop in temperatures and increasing the risk of frost [1].
This weather event is significant because the sudden arrival of polar air can damage crops and disrupt infrastructure in the South and Southeast regions. The system was driven by an extratropical cyclone that pushed cold air deep into the country [2].
Meteorologists reported that the temperature drop began on June 16 [1]. This occurred shortly before the official start of winter on June 21 [1]. Earlier warnings regarding the potential for frost in the South had been issued as far back as May 28 [3], with broader forecasts for the South and Southeast appearing on May 19 [4].
"A mass of cold air causes a drop in temperatures in the Center-South of Brazil, increasing the risk of frosts in São Paulo, Minas Gerais and the Serra da Mantiqueira," the Clima Extremo team from O Globo said [5].
The National Institute of Meteorology, known as INMET, highlighted specific risks for several cities in Rio Grande do Sul. INMET said there is a possibility of intense rain and isolated hail in Porto Alegre, Santa Maria, Pelotas, and Uruguaiana [6].
While the South faced severe cold, conditions in other areas varied. Reports from O Globo indicated that by June 17, weather in Rio de Janeiro remained stable with mild temperatures [5], though a previous report from May 28 noted that the same cyclone system had brought wind-driven rain to the city [3].
"Winter begins next Sunday (21) and this Tuesday (16) there is a chance of frost in areas of the South of the country," the R7 meteorology team said [1].
“A polar air mass moved across southern Brazil in mid-June, bringing a sharp drop in temperatures and increasing the risk of frost.”
The timing of this polar air mass, arriving just before the official winter solstice, underscores the volatility of the region's transition into the coldest season. The involvement of an extratropical cyclone as the primary driver suggests a more aggressive movement of polar air than typical seasonal cooling, increasing the likelihood of agricultural damage due to frost and hail in the critical southern farming belt.
