Hi Philipp,
It's been some time since your question. Hopefully this can still be of some help.
If you have access to MATLAB 2014b or later, you can actually take advantage of the datetime datatype to simplify much of your text parsing and plotting.
I have attached a sample workflow that reads your data as a MATLAB table and plots the temperature with time. The code is much simpler (4 lines without comments). The resulting plot will update itself as you pan or zoom around. You can customize and annotate your plot further to suit your specific needs.