source: Learn English with Let's Talk 2013年05月01日
--Raining cats and dogs: raining heavily
--A fair-weather friend: a friend only in good times
--A ray of sunshine: something/someone which brings happiness or hope
--Have your head in the clouds: unrealistic; out of touch with the real world
--Make hay while the sun shines: a chance to do something good during an opportunity
--Quick as lightning: very fast
--Snowed under: having trouble doing things because of too much work
--Under a cloud: someone who is suspected of doing wrong
--Under the weather: being/feeling very ill
--Weather a storm: come out of a difficult or dangerous situation