The climatic information recorded by the physician Francisco Fernández Navarrete in Granada (southern Spain) during the first third of the 18th century is analyzed in this work. His observations are included in the book Cielo y suelo granadino ('Sky and soil in Granada'), and consist of qualitative comments relating climatic conditions to illness and diseases from 1706 to 1730, as well as instrumental observations (using an “English barometer” and a “Florentine thermometer”) from December 1728 to February 1730. To the best of our knowledge, these are the earliest instrumental observations recorded in Spain. An alternative methodology to Pfister indices, based on the frequency of extreme events, was applied to study this new set of documentary data. The analysis shows that seasonal mean values of temperature and precipitation during the period 1706–1730 were very similar to those of periods of similar length at the beginning of the 20th century, such as 1906–1930. However, some years were especially extreme, such as the dry first half of the 1720s or the winter of 1728–1729 when a strong cold wave affected the city.