Winters are cool with mild temperatures during the day and chilly nights. Highs during the season average  while lows average . Relative humidity averages in the upper 70s%, which means the city is noted for moderate-to-heavy fogs during autumn and winter. July is the coolest month, with an average temperature of . Cold spells originating from Antarctica occur almost every year, and can persist for several days. Occasionally, warm air masses from the north bring warmer temperatures. The lowest temperature ever recorded in central Buenos Aires (Buenos Aires Central Observatory) was  on 9 July 1918. Snow is very rare in the city: the last snowfall occurred on 9 July 2007 when, during the coldest winter in Argentina in almost 30 years, severe snowfalls and blizzards hit the country. It was the first major snowfall in the city in 89 years.