今天是5月5日，立夏啦！從這一刻起，春天徹底和我們告別，夏天正式登場(chǎng)。立夏作為夏天打頭陣的節(jié)氣，可不只是宣告，夏天來(lái)了這么簡(jiǎn)單，老祖宗還流傳下來(lái)一句，“今年三伏天熱不熱，就看立夏”，這讓大家對(duì)今年三伏天的熱度，充滿好奇。

先來(lái)說(shuō)說(shuō)三伏天，它是一年里最熱的時(shí)段，在農(nóng)歷小暑和處暑之間，分初伏、中伏和末伏。按照“夏至三庚數(shù)頭伏”的算法，今年7月20日入伏，8月18日出伏，一共30天 。

那今年三伏天，到底有多熱呢？其實(shí)古人早根據(jù)立夏當(dāng)天的天氣，總結(jié)出了一些預(yù)測(cè)經(jīng)驗(yàn)。像“立夏晴，三伏熱；立夏雨，九場(chǎng)雨”，意思是立夏這天要是大晴天，沒(méi)有下雨，那接下來(lái)的三伏天就大概率干旱炎熱；

要是立夏下雨，那后續(xù)降雨就會(huì)比較多，天氣會(huì)悶熱潮濕些。還有“立夏無(wú)雨三伏熱”“立夏落雨要買(mǎi)傘”等說(shuō)法，表達(dá)的也是類(lèi)似意思，立夏沒(méi)雨，三伏天熱且易干旱；立夏有雨，三伏天降雨多相對(duì)涼爽。

今年立夏在農(nóng)歷四月初八，屬于“月頭”。民間有“立夏在月頭，三伏熱死牛”的說(shuō)法，認(rèn)為月初立夏對(duì)應(yīng)的三伏天會(huì)酷熱。

不過(guò)從現(xiàn)代氣象統(tǒng)計(jì)來(lái)看，立夏日期和三伏天的氣溫，相關(guān)性不太明顯，畢竟氣候是個(gè)復(fù)雜的大系統(tǒng)，受大氣環(huán)流、海洋溫度等，好多因素共同影響 。

除了晴雨，立夏時(shí)的風(fēng)力和風(fēng)向，也能透露點(diǎn)三伏天的天氣信息。北方有“立夏刮北風(fēng)，伏里旱”的說(shuō)法，要是立夏刮北風(fēng)，三伏天，可能會(huì)干旱；而南方則是“立夏刮南風(fēng)，伏里澇”，立夏刮南風(fēng)，會(huì)帶來(lái)暖濕氣流，讓三伏天，雨水偏多，出現(xiàn)悶熱桑拿天。

另外，古人還會(huì)觀察動(dòng)植物的反應(yīng)，來(lái)預(yù)判暑熱。比如“立夏蟬早叫，三伏天里烤”，如果立夏前后蟬鳴提前，那可能預(yù)示著夏季溫度偏高。

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今年南方部分地區(qū)，已經(jīng)出現(xiàn)早蟬，這是不是和全球變暖導(dǎo)致物候，提前有關(guān)呢？

國(guó)家氣候中心預(yù)測(cè)，2025年厄爾尼諾現(xiàn)象，可能會(huì)持續(xù)，受它影響，我國(guó)中東部地區(qū)，夏季氣溫偏高的概率，比較大，華北、黃淮等地可能出現(xiàn)階段性高溫?zé)崂恕?/p>

從長(zhǎng)期趨勢(shì)看，近30年我國(guó)三伏天，平均高溫日數(shù)呈上升趨勢(shì)，極端高溫事件，頻率也在增加，這和全球變暖的“溫室效應(yīng)累加，”以及城市化的“熱島效應(yīng)”，都脫不了干系 。

按照這些農(nóng)諺和氣候預(yù)測(cè)，今年三伏天，或許是北方高溫強(qiáng)度大，南方悶熱持續(xù)久。不過(guò)雖說(shuō)農(nóng)諺，是老祖宗長(zhǎng)期觀察自然，總結(jié)出來(lái)的寶貴經(jīng)驗(yàn)。

但現(xiàn)代氣候太復(fù)雜，受多種因素影響，僅靠立夏的情況，很難精準(zhǔn)預(yù)測(cè)三伏天到底有多熱。咱們還是得結(jié)合現(xiàn)代氣象科技的預(yù)報(bào)，提前做好應(yīng)對(duì)準(zhǔn)備，不管三伏天是熱還是相對(duì)涼爽，都能舒舒服服度過(guò)。