The increase in global air temperature is evident. Such increase is related to human actions, which have a direct impact on environmental diversity, agricultural activities, energy sector, health, transportation, among others. The increase in air temperature associated with climate change will impact the survival of the entire local ecosystem in semi-arid regions. The Brazilian semi-arid region is part of eleven states and has low and concentrated rainfall rates and high temperatures as main characteristics. The traditional Mann-Kendall test quantified by Sen's slope was applied in historical series of average air temperature data provided by the National Institute of Meteorology (INMET) to check the existence of trends in the data. A new method based on cluster analysis has been applied for a deeper understanding of the trends. Significant trends of increase in average air temperature were observed in the annual comparison for 36 weather stations. With the new method based on cluster analysis, it was observed that for most stations the most recent years showed an increase in the average air temperature, in the annual, quarterly and monthly evaluations. The impacts of these increases in air temperature are negative for the local economic and energy sectors and may affect the entire semi-arid region.