smog (or nefos as the Athenians used to call it) has become less common. Measures taken by the Greek authorities throughout the 1990s have improved the quality of air over the Attica Basin. Nevertheless, air pollution still remains an issue for Athens, particularly during the hottest summer days. In late June 2007, the Attica region experienced a number of brush fires, including a blaze that burned a significant portion of a large forested national park in Mount Parnitha, considered critical to maintaining a better air quality in Athens all year round. Damage to the park has led to worries over a stalling in the improvement of air quality in the city. The major waste management efforts undertaken in the last decade (particularly the plant built on the small island of Psytalia) have greatly improved water quality in the Saronic Gulf, and the coastal waters of Athens are now accessible again to swimmers. Safety Athens ranks in the lowest percentage for the risk on frequency and severity of terrorist attacks according to the EU Global Terrorism Database (EIU 2007–2016 calculations). The city also ranked 35th in Digital Security, 21st on Health Security, 29th on Infrastructure Security and 41st on Personal Security globally in a 2017 The Economist Intelligence Unit report. It also ranks as a very safe city (39th globally out of 162 cities overall) on the ranking of the safest and most dangerous countries. As May 2022 the crime index from Numbeo places Athens at 56.33 (moderate), while its safety index is at 43.68. According to a Mercer 2019 Quality of Living Survey, Athens ranks 89th on the Mercer Quality of Living Survey ranking. Climate Athens has a hot-summer Mediterranean climate (Köppen climate classification: Csa). Athens is the hottest city in mainland Europe and according to the Hellenic National Meteorological Service the Athens Basin is also the warmest area of Greece with an average annual temperature of . The dominant feature of Athens' climate is alternation between prolonged hot and dry summers and mild, wetter winters with moderate rainfall. With an average of of yearly precipitation, rainfall occurs largely between the months of October and April. July and August are the driest months when thunderstorms occur sparsely. Furthermore, some coastal areas such as Piraeus in the Athens Riviera, have a hot semi-arid climate (BSh) according to the climate atlas published by the Hellenic National Meteorological Service. However, places like Elliniko,