I've heard that Trump's team is blaming the weather for shit turnout. Because apparently 58 degrees and light rain is a much bigger obstacle than the below freezing temperatures Obama had.
I should also point out that the (early) estimates are between 10,000 and 250,000. For perspective, Obama's 2013 inauguration had over a million people, while his 2009 inauguration reached over 1.8 million people.