The climate becomes progressively drier towards the north of the peninsula. In the north, the annual mean temperature is 27 °C  in Mérida. Average temperature in the peninsula varies from 24 °C  in January to 29 °C  in July. The lowest temperature on record is 6 °C . For the peninsula as a whole, the mean annual precipitation is 1,100 millimetres . The rainy season lasts from June to September, while the dry season runs from October to May. During the dry season, rainfall averages 300 millimetres ; in the wet season this increases to an average 800 to 900 millimetres . The prevailing winds are easterly and have created an east-west precipitation gradient with average rainfall in the east exceeding 1,400 millimetres  and the north and northwestern portions of the peninsula receiving a maximum of 800 millimetres . The southeastern portion of the peninsula has a tropical rainy climate with a short dry season in winter. Petén has a hot climate and receives the highest rainfall in all Mesoamerica. The climate is divided into wet and dry seasons, with the rainy season lasting from June to December, although these seasons are not clearly defined in the south;  with rain occurring through most of the year. The climate of Petén varies from tropical in the south to semitropical in the north; temperature varies between 12 and 40 °C , although it does not usually drop beneath 18 °C . Mean temperature varies from 24.3 °C  in the southeast to 26.9 °C  in the northeast. Highest temperatures are reached from April to June, while January is the coldest month; all Petén experiences a hot dry period in late August. Annual precipitation is high, varying from a mean of 1,198 millimetres  in the northeast to 2,007 millimetres  in central Petén.. Which happens first in the year, the dry season or the rainy?