(1) The winter in Okinawa is warmer than that in Taiwan.
(2) Summertime in Okinawa lasts longer than that in Taiwan.
I've never heard that construction used for comparing the same thing to itself. I wouldn't use it.
1. It is warmer in Okinawa in winter than it is in Taiwan. (The second winter is understood.)
2. Summertime lasts longer in Okinawa than it does in Taiwan.