夏至 Summer Solstice
Worldwide, interpretation of the event has varied among cultures, but most recognize the event in some way with holidays, festivals, and rituals around that time with themes of religion or fertility.[9] In some regions, the summer solstice is seen as the beginning of summer and the end of spring. In other cultural conventions, the solstice is closer to the middle of summer.
夏至
是二十四节气之一，在每年公历6月20或21或22日。夏至这天，太阳运行至黄经90度（夏至点，目前处在双子座），太阳直射地面的位置到达一年的最北端，几乎直射北回归线，此时，北半球各地的白昼时间达到全年最长。对于北回归线及其以北的地区来说，夏至日也是一年中正午太阳高度最高的一天。在北京地区，夏至日白昼可长达15小时，正午太阳高度高达73°32′。这一天北半球得到的太阳辐射最多，比南半球多了将近一倍。
天文专家称，夏至是太阳的转折点，这天过后它将走“回头路”，阳光直射点开始从北回归线向南移动，北半球白昼将会逐日减短。夏至日过后，北回归线及其以北的地区，正午太阳高度角也开始逐日降低。同时，夏至到来后，夜空星象也逐渐变成夏季星空。
The summer solstice (or estival solstice), also known as midsummer, occurs when a planet's rotational axis, or geographic pole on either its northern or its southern hemisphere, is most inclined toward the star that it orbits. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. (Likewise, the Sun's declination from the celestial equator is +23.44° in the Northern Sky and −23.44° in the Southern Sky.) This happens twice each year (once in each hemisphere), when the Sun reaches its highest position in the sky as seen from the north or south pole.
The summer solstice occurs during the hemisphere's summer. This is the northern solstice in the Northern Hemisphere and the southern solstice in the Southern Hemisphere. Depending on the shift of the calendar, the summer solstice occurs some time between June 20 and June 22 in the Northern Hemisphere and between December 20 and December 23 each year in the Southern Hemisphere. The same dates in the opposite hemisphere are referred to as the winter solstice.
As seen from a geographic pole, the Sun reaches its highest altitude of the year on the summer solstice. It can be solar noon only along that longitude, which at that moment lies in the direction of the Sun from the pole. For other longitudes, it is not noon. Noon has either passed or has yet to come. Hence the notion of a solstice day is useful. The term is colloquially used like "midsummer" to refer to the day on which solstice occurs. The summer solstice day has the longest period of daylight, except in the polar regions, where daytime remains continuous for 24 hours every day during a period ranging from a few days to six months around the summer solstice.
风俗活动
祭神祀祖：夏至时值麦收，自古以来有在此时庆祝丰收、祭祀祖先之俗，以祈求消灾年丰。因此，夏至作为节日，纳入了古代祭神礼典。《周礼·春官》载：“以夏日至，致地方物魈。”周代夏至祭神，意为清除荒年、饥饿和死亡。夏至日正是麦收之后，农人既感谢天赐丰收，又祈求获得“秋报”。夏至前后，有的地方举办隆重的“过夏麦”，系古代“夏祭”活动的遗存。
消夏避伏：夏至日，妇女们即互相赠送折扇、脂粉等什物。《酉阳杂俎·礼异》：“夏至日，进扇及粉脂囊，皆有辞。”“扇”，借以生风；“粉脂”，以之涂抹，散体热所生浊气，防生痱子。在朝廷，“夏至”之后，皇家则拿出“冬藏夏用”的冰“消夏避伏”，而且从周代始，历朝沿用，进而成为制度。
“夏至”食品
“麦粽”与“夏至饼”：江南食俗，一般有麦粽、角黍、李子、馄饨、汤面等。《吴江县志》：“夏至日，作麦粽，祭先毕，则以相饷。”不仅食“麦粽”，而且将“麦粽”作为礼物，互相馈赠。夏至日，农家还擀面为薄饼，烤熟，夹以青菜、豆荚、豆腐、及腊肉等，祭祖后食用，俗谓“夏至饼”，或分赠亲友。
冬至馄饨夏至面：自古以来，中国民间就有“冬至馄饨夏至面”的说法，江南一带夏至吃面是很多地区的重要习俗，民间有“吃过夏至面，一天短一线”的说法。南方的面条品种多，如阳春面、干汤面、肉丝面、三鲜面、过桥面及麻油凉拌面等，而北方则是打卤面和炸酱面。“因夏至新麦已经登场，所以夏至吃面也有尝新的意思。”
气候特点
夏至对流天气
夏至以后地面受热强烈，空气对流旺盛，午后至傍晚常易形成雷阵雨。这种热雷雨骤来疾去，降雨范围小，人们称“夏雨隔田坎”。唐代诗人刘禹锡，曾巧妙地借喻这种天气，写出“东边日出西边雨，道是无晴却有晴”的著名诗句。对流天气带来的强降水，不都像诗中描写的那么美丽，常常带来局地灾害。诗人徐书信“在暑雨”一诗中，也对夏日雷雨天气进行了恰如其分的描述：“夏日熏风暑坐台，蛙鸣蝉噪袭尘埃。靑天霹雳金锣响，冷雨如钱扑面来。”
夏至暴雨天气
多数情况，“夏至”期间，正值长江中下游、江淮流域梅雨，频频出现暴雨天气，容易形成洪涝灾害，甚至对人民生命财产造成威胁，应注意加强防汛工作。
夏至江淮梅雨
江淮梅雨
夏至时节正是江淮一带的“梅雨”季节，这时正是江南梅子黄熟期，空气非常潮湿，冷、暖空气团在这里交汇，并形成一道低压槽，导致阴雨连绵的天气。在这样的天气下，器物发霉，人体也觉得不舒服，一些蚊虫繁殖速度很快，一些肠道性的病菌也很容易滋生。这时要注意饮用水的卫生，尽量不吃生冷食物，防止传染病发生和传播。
夏至高温天气
夏至和冬至一样，都是反映四季更替的节气。天文学上规定，夏至为北半球夏季的开始。夏至过后，虽然太阳直射点开始从北回归线逐渐向南移动，北半球白昼开始逐渐变短，对于北回归线及其以北的地区，正午太阳高度也开始逐日降低，但由于太阳辐射到地面的热量仍比地面向空中散发的多，故在以后的一段时间内，气温将继续升高，因此有“夏至不过不热”的说法。从1951年～2006年的资料来看，北方许多城市的历史极值都出现在夏至后。
