The 33-year-old singer had Summer by C-section on Saturday, August 16.
The little girl is Christina's first child with fiancé Matt Rutler, but she is already proud mum to six-year-old son Max, from her relationship with ex-husband Jordan Bratman.
Christina and Matt, a film production assistant, were obviously very happy with the weather – poor Summer Rain could well have been named Foggy Breeze or Autumn Drizzle if the day hadn't been in her favour...
So proud to welcome our beautiful daughter Summer Rain Rutler into the world.
- Christina Aguilera (@xtina) August 18, 2014
According to our baby name finder, the name Summer has a literal meaning of 'born in the summer'.
Rain is a girl's name meaning Strong. According to the Office of National Statistics' review of the most popular baby names for 2013 in the UK, Summer (number 48 in the annual rankings) reached number 23 in July, but fell to number 94 in December.
Christina announced her pregnancy in March, a month after getting engaged to Matt.
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Just before her daughter arrived, Christina posed nude for V magazine. In an interview to accompany the photos, Christina said: "As a woman, I'm proud to embrace my body through all stages of life, staying fearless and confident in surrendering to the unknowns the future has in store."
In July, before the nude pictures were taken, the then mum-to-be was the guest of honour at a swanky baby shower in LA.
Guests enjoyed pink champers and tucked into a graphic baby shower cake, with icing which read: 'Push X-Tina, push!'
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