The last few years we’ve noticed tick activity starting earlier and earlier, most likely due to our mild winters. Considering how mild and warm it’s been, we expect tick activity to start up early again this year.
The University of Kentucky mentioned earlier this winter that there are two species of ticks that actually remain active throughout the winter, and will be moving and seeking prey any time the temperature is above freezing (https://kentuckypestnews.wordpress.com/2017/01/24/two-species-of-ticks-active-during-kentucky-winters/. Of the two, only one of them is commonly a pest of domestic pets and humans: the black-legged tick, also known as the deer tick. As you may know, deer tick are infamous for spreading Lyme disease.
You can read more about tick biology, development, and control in this Purdue bulletin: https://extension.entm.purdue.edu/publications/E-71.pdf . An article on Lyme disease is available here: http://extension.entm.purdue.edu/publications/E-244.pdf .