I suspect mempool grows at the end of each month and today is the last day of the month. Maybe just a coincidence, but I send coins on 30th or 31th of each month on a regular basis and mempool is almost always congested. Need to check the graphs to make sure though.
Here's
the graph:

I don't see a clear increase in fees at the end of each month. At the end of November and January it went up a bit, but nothing more than what happens in other parts of the months too.