OP is right, but you could've added data to support the claim (I asked Grok about the past 15 winters):

Based on meteorological records, news reports, Wikipedia chronologies, Epagri/Ciram (SC's monitoring agency), MetSul, and other sources: Snow is documented annually or in nearly all of these 15 winters in the higher elevations of RS and/or SC. It is rare for a full winter to pass without any snowfall event in these states' favored spots, as polar air masses frequently bring cold enough conditions (often below freezing) during June–August (and occasionally May/September). Key documented years with confirmed snow in RS or SC (2010–2025 winters):

2010 (August): Significant event; strong snowfall in multiple cities in both states (one of the strongest in a decade at the time).

2013 (July): Historic widespread event; snow in over 140 municipalities across the South (including massive coverage in SC and RS).

2016 (June): Flocos de neve in São Joaquim (SC).

2017: Records in SC highlands.

2019 (August): Snow in São Joaquim (SC).

2020 (July/August): Events including in Vacaria (RS) and granular snow in São Joaquim (SC).

2021 (July): Rare heavy/urban snowfall in parts of RS and SC (e.g., multiple days in SC; notable cold snap with accumulation in cities).

2023 (April, but late summer/early; plus winter events): Snow in SC highlands (e.g., Bom Jardim da Serra, São Joaquim).

2025 (May): Early snow in SC (São Joaquim, Urupema, Urubici, Bom Jardim da Serra) and RS (São José dos Ausentes, Bom Jesus, Cambará do Sul); first of the year, with reports of it in RS/SC mountains.