Climate change is considered as one of the main environmental concerns of the 21st century. Increased variation and changes in mean temperature and precipitation are expected to dominate future changes in climate, and affect crop productivity. It is highly important to identify regions vulnerable to climate change and identify suitable adaptation practices that can sustain productivity to some extent. In this study, an iterative chi-square method was applied to detect recent possible climate change in extreme daily minimum and maximum temperatures for five different regions (Birjand, Boujnord, Mashhad, Sabzevar and Torbat heydarieh) of Khorasan province in Iran between a 15-year recent period and a 30-year prior period. The method determines the values of extreme daily temperature that are most significantly different between the prior and recent periods and gives a measure of the weekly significance of that difference. Determination was made of the percentage change in the frequency of the number of extreme days for each period of continuous significant weeks. In all five regions, a few days of extreme low minimum temperature (especially in Mashhad and Sabzevar) was experienced during the recent period. The major changes in climate for minimum temperature were determined in Mashhad. In this region the highest percentage change of climate (minimum temperature) occurred during week 33 when a 41% decrease of extreme low minimum temperatures occurred. In Mashhad the highest warming (decrease in days of minimum temperature) occurred during late March to late December. Among five regions, for maximum temperatures, during the recent period some weeks were experienced a greater number of days of extreme high maximum temperature (except Torbat heydarieh and Birjand). In Torbat heydarieh, the highest percentage change of climate occurred during week 24 when 26% decrease of extreme high maximum temperatures were detected. In Torbat heydarieh the highest cooling occurred during April to early December.

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