Yesterday was a foggy day but different to that 2 days before

Yesterday was another foggy day. Unlike the previous foggy day which cleared to a brilliant blue sky, this cleared to a dull, dank day with the conditions not changing all day. Here are 2 photos of a tree that I regularly photograph from my back garden:

A tree in the fog at the start of the day
The same tree 30 minutes later when the fog had cleared

I took further photographs throughout the day but they were just the same as the last one with the dull conditions lasting throughout the day. Here is a before/after version showing the fog clearing:


[caption id="attachment_6255" align="aligncenter" width="600"] A tree in the fog at the start of the day[/caption]

[caption id="attachment_6254" align="aligncenter" width="600"] The same tree 30 minutes later when the fog had cleared[/caption]

In the first image you can just make out a bird (rook?) sitting at the very top of the tree…