Climate: Many associate Alajuela with the warm and sunny climate that characterizes the city. However, the vast majority of the provincial territory lies on the other side of the volcanic cordilleras, extending north to the Nicaraguan border. This sprawling area in the northern lowlands is under the influence of weather conditions coming in off the Caribbean Sea and was formerly covered in extensive tracts of majestic rain forest. Recent agricultural colonization of the northern frontier has severely altered the natural landscape (witness the paucity of national parks in the region), and very likely has affected the climate to some degree, Even wetter, and much cooler, conditions exist along the Caribbean-facing slopes of the cordilleras, which reach a height of 2,704 meters above sea level on the summit of Poás Volcano.

History: Following the establishment of the city of Cartago in the latter part of the 16th century, the incipient population began expanding westward. By the beginning of the 18th century, the population of Heredia had grown such that it became a second base of expansion, again to the west.

The settlement of the northern portion of this province only began in earnest in the later half of the 19th century, and even so did not reach great proportions until the second half of the 20th century owing largely to the difficult access. In fact, much of the original colonization (apart from that of the Botos tribes who had inhabited the region for centuries prior to the coming of the Spaniards) came not from Costa Rica, but from Nicaragua since numerous navigable rivers flow north from their origins in the cordilleras and empty into either Lake Nicaragua or the San Juan River. This natural geographic connection was used (and to some extent still is today) by people coming from Nicaragua in search of new land or for exploiting forest products (e.g., hunting, rubber tapping, and extracting ipecac root).

In the last few decades, with an extensive network of all-weather roads constructed in this once isolated region, cattle and crop production have come to dominate the countryside and a thriving agricultural economy now exists which supplies much of the nation's corn, beans, and fruit and vegetable produce.