Low R-squared and Trend


This is my first contact with this forum!

From 14 years of January temperature data, I created a graph. (some red been seen behind the black yearly average line - indicating imputations in New Average.) minute data so 1440*31 every year... I have done this statistics for 4 consecutive months and seen the same low r2, but trends go either way. Januari 2019.png

We have discussed a bit about the low R-squared value and the trend line and interpreted them a bit differently.

Does the low R-squared value indicate that the trend is meaningless, or does it just mean one cannot predict the future (f ex next year would be -7.1 and not very probable...). I have read that how you interpret low r2 is dependent of what types of data, et c, you have. How about this type of weather data?