It was winter 5 months later in Tianjin. Take warm clothes. The average temperature in Jan is below zero. I guess there is no direct flight from India to Tianjin. You can get to Beijing first and then take airport bus to Beijing South Railway Station to catch intercity bullet trains (train number begins with letter C). Then you can get to Tianjin 30 minutes later.
Capital airport to Beijing south railway station is not very convenient by far. You should take airport bus or express train to Dongzhimen and then change to Subway Line 2 to Chongwenmen then change to Line 5 to the train station. Or you can take the airport bus line to Fangzhuang, then take a taxi to the railway station (taxi fare about 15RMB). Hope it make sense.