My 23 month old baby has a fever after taking cold/tap water for bath?

i gave her a not too cold, water just came out from the faucet,(coz i used to boil water for her bath) and now tonight she has a fever, 38 c, what was wrong with that? i bathe her around 2pm. its summer here in my country so i thought its ok to give her bath in the afternoon. but apparently, shes having a fever now.. pls need advice. thanks:(