The Mediterranean Region is the major area devoted to olive tree crop,and therefore a study of olive flowering is of great interest for the European Community. On the otherhand, olive pollen is one of the main causes of pollen allergy in the Mediterranean area. Olive floweringis affected by climatic factors such as temperature and photoperiod, which vary geographically in latitudeand altitude. Temperature has been used to study those processes that lead to flowering in the olivetree. The aim of the present paper is firstly the comparison of the flowering full bloom dates in twoMediterranean areas, Sicily (Italy) and Cordoba (Spain), located in the same latitudinal band (37-38degrees N) and to calculate the heat requirement until flowering by determination of different threshold temperatures and methods of heat accumulation. A delay of the full flowering dates in the Spanish comparedwith the Italian olive groves was observed. The most suitable threshold temperatures were carried outin a 7 degrees -15 degrees C range by considering the heat accumulation start on 1 January in each olivegrove. In particular, some causes were indicated as responsible for the different threshold temperaturesrecorded in the 2 study areas: First, the different climatic conditions (continental and insular climate) secondly the different cultivars present in the olive groves.