Chattanooga on the whole is quite mild and temperate (excluding the Summer months). You can expect the temperature to be around fourty degrees farenheit in January building to the high eighties and nineties in July and then back down again. 
Spring and Fall are beautiful with weather in 50s, 60s, & 70s. Rain varies significatnly but is usually between three to five inches a month, and of course in the Winter months sometimes that means snow!