含氧量降低
The gentle sounds of the rain, cloudy sky and slight drop in temperature on a rainy day all give a sleeper-friendly vibe and make people want to stay in bed for a little while longer.
溫柔的雨聲、陰沉的天空以及略降的溫度都構成了讓人好眠的氛圍，讓人想多賴在床上一會兒。
gentle(adj.)溫柔的slight(adj.)些微的sleeper-friendly(adj.)好睡的vibe(n.)氛圍=atmospherea relaxing atmosphere令人放鬆的氛圍
But why is that?
但為什麼會這樣呢？
An Australian study shows that the negative ion content in the air increases when it rains.
有項澳洲研究指出，下雨時空氣中的負離子含量會增加。
negative ion負離子negative(adj.)負、負數的a negative comment負面評價content(n.)含量;內容a table of contents(書)目錄increase(v.)增加decrease(v.)減少
Negative ions have a calming, soothing and even hypnotizing effect.
負離子有鎮靜、安撫甚至催眠的效果。
calming(adj.)鎮靜的soothing(adj.)舒緩的hypnotizing(adj.)催眠的hypnotize(v.)催眠=put sb. to sleepeffect(n.)效果
Also, increased water vapor in the air lowers the air pressure and oxygen level, which in turn makes people feel drowsy and want to hit the hay.
此外，空氣中的水汽增加會降低氣壓以及含氧量，讓人們感到昏昏沈沈，並想倒頭大睡。
increased(adj.)增加的water vapor水汽vapor(n.)蒸汽lower(v.)使降低air pressure大氣壓力oxygen(n.)氧氣oxygen level含氧量in turn因此;於是drowsy(adj.)昏沉的sleepy(adj.)想睡的hit the hay睡覺=catch some Zs=go to bed=go to sleeptake a nap小睡片刻=take a siesta
What’s more, people tend to stay in when it rains.
而且下雨天大家通常都容易待在家裡。
What’s more此外=what is more=moreover=furthermoretend to傾向~容易~tend to sleep early容易早睡stay in待在家中=stay at home
With not much to do at home, turning in sounds like a good option.
既然在家沒有什麼事可做，許多人就會想睡覺補個眠。
turn in睡覺= go to sleep=hit the hayoption(n.)選項=choice
Although rains may make a good night’s (or day’s) sleep, the drop of oxygen level in the air doesn’t necessarily mean that people will wake up refreshed or energized later.
雖然雨天或許可帶來一夜（或一日）好眠，但是空氣中的含氧量降低，可不一定代表醒來後會覺得神清氣爽或充滿活力。
although(conj.)雖然=thoughnot necessarily 不一定refreshed(adj.)(人感到)神清氣爽的比較refreshing(adj.)令人神清氣爽的a refreshing cold drinkenergized(adj.) (人感到)精神飽滿energize(v.)使…充滿活力;使振作Energizer 勁量電池（商標名）
However, after understanding these reasons why they feel extra sleepy on rainy days, people may be able to combat the drowsiness next time when it rains.
不過，在了解為什麼雨天特別想睡的原因後，人們或許可以在下回下雨時打擊睡意。
combat(v.)打擊=fightdrowsiness(n.)昏沉drowsy(adj.)昏昏沈沈的