Don't worry ,many spring bulbs start growing underground in August and show above any time from Oct onwards. We have our first daffodils showing but the bulbs are perfectly hardy under ground and the tops may go a little yellow but soon green up. I was going to take a photo of the daffs today ,as many do worry about them being early but this is quite normal. If the bulbs were in pots remember they can get frozen through the sides and then they will die.