The road from Kanyakumari to Trivandrum is very straighforward. First you need to take the State Highway 179 till you reach Kappukad Irenipuram road. From there you need to take the MDR 216 till you reach National Highway 66. You then need to continue on National Highway 66 till you reach your destination.
Trivandrum is a coastal city and although summer temperatures do not go beyond 35 degree Celsius the humidity level in the air makes it very uncomfortable for you to travel. It could come in the way of your travel plans. Unless you plan on renting an air conditioned cap it will be very difficult for you to get from one place to another during the summers. Trivandrum receives the highest rainfall and the humidity makes it even more difficult for you to get around town. There also some torrential rain bursts that Trivandrum is famous for. So you might want to stay away from the city during the monsoons. Winters in Trivandrum are the best and while the temperature doesn't drop very low, it becomes as cold as 15 degree Celsius making it an ideal place for you to visit during the winter.
There are three routes to get from Kanyakumari to Trivandrum. All three routes have the same travel time. The first route is via State Highway 179 and National Highway 66. The second route is via State Highway 179. The third route is via National Highway 66.
In order for you to get to Trivandrum from Kanyakumari you will have to take the national highway which is well maintained. It is a straight road and there is no twist and turn around it making it a comfortable journey.