The song received very positive reviews from most critics. Nick Levene from Digital Spy gave to the song 4 stars (out of 5) and said: "Those unconvinced that much had changed when Mika returned with 'We Are Golden' this summer should be pleasantly surprised by 'Rain', the second single from his second album. The shrieking has been reined in, the nursery rhyme hooks have been ditched and instead we're treated to a concoction of shimmering synths, layered vocals and throbbing, clubby beats. As it builds towards a crescendo that's both intriguingly dark and glitteringly magical, Mika proves he's perfectly capable of channelling his hyperactivity in the right direction. Here's hoping for more of this in the future".Heather Phares from Allmusic says that "Rain" is a kissing cousin to "Relax"'s pulsing, melancholy disco-pop.
The music video for "Rain" was filmed in Epping Forest in Essex and premiered online on 16 October 2009. It was directed by Nez Khammal. The video is set in a dark enchanted forest with Mika waking up in a colourful tent. He is soon joined by various strangely dressed imps and creatures who dance around him at first but chase him out of the forest amid exploding fireworks.