6100 BC a tsunami caused by the Storegga Slide hit Shetland, as well as the west coast of Norway, and may have created a wave of up to high in the voes where modern populations are highest. The highest point of Shetland is Ronas Hill at . The Pleistocene glaciations entirely covered the islands. During that period, the Stanes of Stofast, a 2000-tonne glacial erratic, came to rest on a prominent hilltop in Lunnasting. Shetland has a national scenic area which, unusually, includes a number of discrete locations: Fair Isle, Foula, South West Mainland (including the Scalloway Islands), Muckle Roe, Esha Ness, Fethaland and Herma Ness. The total area covered by the designation is 41,833 ha, of which 26,347 ha is marine (i.e. below low tide). In October 2018, legislation came into force in Scotland to prevent public bodies, without good reason, showing Shetland in a separate box in maps, as had often been the practice. The legislation requires the islands to be "displayed in a manner that accurately and proportionately represents their geographical location in relation to the rest of Scotland", so as make clear the islands' real distance from other areas. Climate Shetland has an oceanic temperate maritime climate (Köppen: Cfb), bordering on, but very slightly above average in summer temperatures, the subpolar variety, with long but cool winters and short warm summers. The climate all year round is moderate owing to the influence of the surrounding seas, with average night-time low temperatures a little above in January and February and average daytime high temperatures of near in July and August. The highest temperature on record was on 6 August 1910 at Sumburgh Head and the lowest in the Januaries of 1952 and 1959. The frost-free period may be as little as three months. In contrast, inland areas of nearby Scandinavia on similar latitudes experience significantly larger temperature differences between summer and winter, with the average highs of regular July days comparable to Lerwick's all-time record heat that is around , further demonstrating the moderating effect of the Atlantic Ocean. In contrast, winters are considerably milder than those expected in nearby continental areas, even comparable to winter temperatures of many parts of England and Wales much further south. The general character of the climate is windy and cloudy with at least of rain falling on more than 250 days a year. Average yearly precipitation is , with November