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Airborne pollen calendars are useful to estimate the flowering season of the different plants as well as to indicate the allergenic potential present in the atmosphere at a given time. In this study, a 1-year survey (from January 2013 to February 2014) is presented of the atmospheric concentration of pollen types in Guarda (Portugal), using a 7-day Hirst volumetric trap. The daily mean concentration of both the number of pollen grains and the main pollen season was determined as well as the bi-hourly variations. The highest airborne pollen concentration was found during early spring and early summer. Contrastingly, December was the month with the lowest pollen concentration. The major pollens sampled were Quercus, Pinaceae, Poaceae, Cupressaceae, Urticaceae, Apiaceae, Oleaceae and Polygonaceae. Some differences were found in the intradiurnal distribution patterns of the pollen types studied, with some taxa types being predominantly sampled in the morning (8:00-10:00 a.m.) while others were more evident in the late evening hours (8-10 p.m.). Finally, these results were compared with the forecast made by the Portuguese Aerobiology Network for the central region of Portugal, revealing some significant differences in the pollination periods.