Interesting. You may copy the graphic of the main result to the beginning of the page with these data, something like a long tl;dr with two or three paragraphs.
Reformatting all the article and graphs is a lot of work, specially if the main objective is other. But a nice abstract with the main result helps the reader to understand what is the interesting part and find it with all the details later.
Out of interest, what if anything would you say the main result is? I don't have one in mind, which I think harms the post - there's no narrative, just a bunch of questions and answers. The three final plots are there because the spec required them, and I chose them more because the plots themselves seemed interesting than for the questions they answered.
But you're right that an abstract would have helped, and I feel a little embarrassed that I didn't think to include one myself. Even without a single main result, I could have included a short list of interesting findings.
(For a blog post) You can declare whatever you like as the main result. I think that the % of the reduction of the bike use by the rain is good candidate. Choose a nice small fact that you can tell to your friend during lunch. Think about the linkbait version: "You can't believe how much the bike use is reduced by rain ..." but please use a non linkbait title, because I hate them.
Usually the biggest change is a good candidate. For example "Moon phase reduce the bike use a 0.027% with p<.99" is a very bad selection.
When you have more time, I think that classifying the rainy days as "small drizzle" and "heavy thunderstorm" will make the changes bigger. I've never been there, but London if not famous for being sunny, so I guess people just ignore the drizzle.
Reformatting all the article and graphs is a lot of work, specially if the main objective is other. But a nice abstract with the main result helps the reader to understand what is the interesting part and find it with all the details later.