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On the other extreme, freezing temperatures are common between mid-November and late March. In some years, however, frosts may occur as late as early May. Temperatures below −10 °C are, especially in recent years, only seen on rare occasions. The city lies within the warmer extent of the 8a USDA plant hardiness zone (−12.2 to −9.4 °C or 10 to 15 °F). Some winters may pass without a frost below −5 °C (data from the nearest active climate station). These comparably mild conditions in Winter permit the planting of plants that would either not be reliably hardy or not able to bloom throughout Germany like "Trachycarpus" palms, Summer lilac, "Paulownia tomentosa" and Rosemary.