Navigation
There is very little. There's the text box in the middle of the page, and smaller links to secondary or related pages, like a blog and terms of service.
Architecture
There's a one layer architecture, with a home page, and various pages that link from it.
Content/Typography
The typography is not great. Text is a little small, aside from the title, and there's a mish-mash of different fonts without much thought. On the upside, I do like that the zipcode is shown in old style figures. The choice of such big fonts for the blog and umbrelletiquette is interesting.
Grid/structure
Everything is stacked on top of each other on the main page, while the blog has a central column with dates sitting on the margin.
Iconography/imagery
The umbrella is appropriate and well rendered, but there might be a few too many raindrops
Color Palette
It's a little too blue, but blue is not an extremely loud colour.
Site Focus
What I like about this site is that it does one thing, but it does it well. It's a great idea for people who need to know that one aspect of the weather every day.