Cold water and flour Does flour and water of 45 degrees Fahrenheit rise? I thought that it has to be warmer, or they wont react at all. 
Will it rise just at a slower paace?
Short answer: it will still rise just slower. Every week when I make bread I make the dough the night before, put it in the fridge (which is about 40 degrees) and use it the next day. The dough usually doubles in size by the morning. 

There is a nice breakdown of the temperate range of yeast at https://www.bobsredmill.com/blog/baking-101/what-temperature-kills-yeast/