How To Use Seasonality Adjustments And Data Exclusions In Google Ads

Smart bidding in Google Ads is an incredibly powerful tool, but it comes with one significant vulnerability: it learns from historical data, and sometimes that data tells the wrong story. If your conversion rates are about to spike because of a seasonal promotion, or if a period of unusual activity has distorted your account's performance signals, the algorithm will not automatically know that. This is precisely where seasonality adjustments and data exclusions come into play, and understanding how to use them correctly can be the difference between your campaigns thriving during key periods or simply spinning their wheels whilst the algorithm catches up too late to matter.

What Seasonality Adjustments Actually Do

Seasonality adjustments are a feature within Google Ads that allow advertisers to tell the smart bidding algorithm to expect a temporary and significant change in conversion rates. They are not a permanent bid modifier; they are a short-term signal designed to prepare the system for an event it would otherwise be blind to.

Google's smart bidding strategies, such as Target CPA and Target ROAS, are constantly analysing historical performance to predict future conversion rates and adjust bids accordingly. The problem is that for a one-off sale event, a product launch, or a flash promotion, there is no historical precedent baked into the recent data window. Without any intervention, the algorithm will likely either underbid during the surge, missing out on valuable traffic, or overspend once it finally recognises the uplift and overcorrects. Seasonality adjustments give you the ability to proactively communicate what is coming rather than waiting for the system to figure it out retrospectively.

You can find seasonality adjustments in Google Ads by navigating to the Tools and Settings menu, then selecting Bid Strategies under the Shared Library section. From there, you will find the Advanced Controls option where seasonality adjustments can be created. Google's own support documentation provides a clear breakdown of the setup process if you need a reference point.

When setting a seasonality adjustment, be realistic with your conversion rate uplift estimate. Overinflating it can cause the algorithm to overbid and exhaust your budget before your promotion even reaches its peak.

When To Use Seasonality Adjustments

These adjustments are specifically designed for short, sharp events, typically spanning no more than a few days at a time. Think of scenarios such as a Black Friday sale running across a long weekend, a limited-time product launch, or a seasonal event tied to your industry. If the change you are anticipating is gradual or long-term, adjusting your target CPA or target ROAS at the campaign level is the more appropriate route.

It is also worth noting that Google recommends using seasonality adjustments primarily for campaigns using Target CPA or Target ROAS bidding strategies. They are less relevant for manual CPC or Maximise Clicks, where the algorithm is not making conversion-based predictions in the same way.

Before a major promotional event, consider what your historical data looks like compared to what you genuinely expect. If you are running a sale that typically drives a significant uplift in conversion rate compared to a standard trading period, feeding that expectation into the system in advance gives the smart bidding algorithm the best possible foundation to perform well throughout that window.

Understanding Data Exclusions

Data exclusions serve a different but equally important purpose. Whilst seasonality adjustments prepare the algorithm for something coming, data exclusions protect it from something that has already happened. Specifically, they allow you to remove a period of flawed or anomalous conversion data from the smart bidding model so that it does not continue to negatively influence future bidding decisions.

Common scenarios where data exclusions become necessary include website outages that prevented conversions from being tracked properly, a broken conversion tag that went unnoticed for a period of time, or an unusual external event that caused temporary and unrepresentative spikes or drops in your data. If smart bidding is left to learn from a period where your checkout page was broken and no sales were recording, it will draw incorrect conclusions and potentially underbid on perfectly good traffic going forward.

Data exclusions can also be found within the Advanced Controls section under Bid Strategies in the Shared Library. You simply define the date range that should be excluded, and Google's algorithm will discount that period when making future bidding calculations.

Always document the reason for any data exclusion you apply. If you are managing an account on behalf of a client or working within a team, having a clear audit trail of when exclusions were applied and why will save a significant amount of confusion further down the line.

How These Features Work Together

The real power of seasonality adjustments and data exclusions comes from using them as a complementary pair within a well-managed account. Before a major sales event, you apply a seasonality adjustment to prime the algorithm. After the event, if the data from that period is so atypical that it would skew the model's learning, you follow up with a data exclusion to prevent that spike from distorting ongoing bidding decisions.

Consider an e-commerce account running a significant promotional event. Conversion rates during the event could be dramatically higher than normal trading. Without a seasonality adjustment beforehand, the algorithm may not capitalise on the traffic surge quickly enough. Without a data exclusion afterwards, the algorithm may continue bidding as though those conversion rates are the new normal, leading to inflated bids and wasted spend once the promotion ends and conversion rates return to their standard level.

Common Mistakes To Avoid

One of the most frequent errors is applying seasonality adjustments to campaigns with limited conversion volume. Google's guidance is clear that these features work best in accounts with sufficient conversion data to support smart bidding in the first place. If your campaign is already struggling to gather enough signals, adding an adjustment on top of an already thin data set can lead to unpredictable bidding behaviour.

Another mistake is treating data exclusions as a routine housekeeping tool rather than a specific remedy for genuine data problems. Excluding too many periods can deprive the algorithm of the very data it needs to learn effectively. Use them deliberately, and only when there is a clear and justifiable reason to do so.

Final Thoughts

Seasonality adjustments and data exclusions are not features you will use every single day, but knowing when and how to deploy them is a mark of a well-rounded Google Ads practitioner. They exist because smart bidding, for all its capability, cannot predict or self-correct around events it has no context for. By using these tools thoughtfully, you are not fighting the algorithm; you are simply giving it the information it needs to do its job properly. Take the time to understand the mechanics behind them, apply them with precision, and your campaigns will be far better equipped to handle the peaks, troughs, and anomalies that every account inevitably encounters.