Most Google updates never get a name or a dashboard entry. MozCast exists to give SEOs a shared reading of the quiet reshuffling that happens beneath every ranking report.
How the thermometer works
Launched in 2012 by Moz marketing scientist Peter J. Meyers, known as Dr. Pete, MozCast crawls a fixed set of keywords every 24 hours and compares each keyword’s top 10 US organic results with the previous day.
The difference becomes a change rate, which Moz multiplies by a constant so an ordinary day lands around 70°F. A reading of 90°F or higher has long been treated as a likely major algorithm change, according to early guidance reported by Search Engine Land. The hottest peaks have hit around 113°F in June 2013 and roughly 122°F during the August 2023 core update.
Third-party guides updated in September 2026 put the current sample at about 10,000 keywords across five major US cities. Moz publishes findings a day in arrears with a 30-day chart and annotations of significant events.
Reading the temperature like an operator
The practical value is the split diagnosis. A traffic drop on a 70°F day points to a site-specific issue: a technical fault, a lost link, a change in crawlability. The same drop on a 110°F day points to an industry-wide shift.
MozCast also operates as corroboration. PPC Land has cited it among a dozen or more trackers during the April 2025 spikes, the June 2025 pre-update turbulence, and the December 2025 core update that ran 18 days from December 11 to 29.
- Domain diversity: how much of the top 10 is spread across unique domains.
- Big 10: the share of results held by the ten most prominent domains.
- EMD and PMD influence: how often exact- and partial-match domains appear.
- SERP features: the prevalence of snippets, video carousels and other non-standard elements.
What the temperature cannot tell you
MozCast measures movement, not cause. It cannot say which sites gained or lost, why, or whether your domain was touched. It samples only the top 10, only US results, and only Moz’s chosen queries.
That narrowness can produce false alarms. On June 26, 2013, MozCast hit 113°F, its hottest reading to that point; other trackers saw normal results and search forums showed no matching spike. Since Google removed the num=100 parameter on September 14, 2025, every scraping tracker also carries more exposure to anti-scraping measures.
Playbook for volatility readings
Use MozCast as a first screen, not a final answer. If it reads hot, cross-check Semrush Sensor, Sistrix, Accuranker and Algoroo before you respond. If it reads normal, audit your own site first.
Google’s confirmed updates are sparser than they used to be. SEO consultant Gagan Ghotra’s analysis, covered by PPC Land in January 2026, found confirmed Google updates fell from 10 a year in 2021 and 2022 to four in 2025, while volatility rose. That makes a consistent external reading more useful, not less.
Source: PPC Land
