MozCast was designed to help you keep track of the day-to-day changes in the Google algorithm.
This tool is awesome and after using it and following it on Twitter (hint, hint) it can actually help explain some of your sites strange analytic occurrences. Google gives public update announcements every so often, but as SEOs we know that these are happening a lot more often than Google will actually admit to. Using MozCast allows you to see the general activity of Google and how it might be affecting your website.
Easy to Understand
MozCast is pretty easy to use too, if the temperature is high or has stormy conditions then there is something going on with the movement of rankings and changes. Allowing for you to see just how often the update are happening with Google and to help put a little more information to maybe be a cause for drops or spikes in analytic data. To use MozCast effectively you need to be aware that the weather given today was actually yesterday’s weather report and not the current day. Unfortunately, Moz can’t predict the future, yet.
It all starts with this: every 24 hours, we track a hand-picked set of 1,000 keywords and grab the top 10 Google organic results. Keywords were deliberately chosen to avoid obvious local intent, are distributed evenly across 5 "bins" by query volume, and are tracked at roughly the same time every day from the same location. In other words, we do our best to keep the data set tightly controlled.
Each day, we take the current top 10 and compare it to the previous day's top 10 (for any given keyword), and calculate a rate of change or "delta". Specifically, we use two metrics – called Delta 100 and Delta10 – which measure the change across the entire set of top 10 results. Then, we crunch Delta10 across all 1,000 keywords and multiply the resulting average by a fixed multiplier (currently, 28.0) to produce something that looks like a temperature (in °F). An average day is about 70°F.