Seasonal mappings help assess the robustness of environments under the most “extreme” conditions.

Regulatory guidelines emphasize seasonal temperature mapping to verify storage conditions across all possible environmental extremes. Summer mapping specifically tests how rising temperatures and increased solar radiation impact controlled environments, something that winter mapping does not fully capture. In summer, issues like radiation heating from the sun can affect temperature control, and performing mappings ensures that your facilities can maintain product integrity under these conditions.

If relevant, failing to conduct a summer mapping study can result in unforeseen temperature excursions, affecting product integrity and potentially leading to compliance issues.

In other words, summer mapping is relevant because:

• High temperatures can impact the stability of stored products.
• Mapping ensures storage conditions remain within required parameters.
• Many regulatory bodies require summer mapping to account for peak seasonal fluctuations.

Also see: Best practices for temperature mapping in GxP

One of the most common questions is whether seasonal mapping is necessary for a given facility. The answer depends on several factors, and, as usual, your risk assessment is your key to determining the need.

Also read: Guidelines for risk-based temperature mapping in GxP

The answer depends on several factors, including but not limited to:

• External temperature fluctuations: If your facility is located in a region where seasonal temperature changes are significant, mapping in both the warmest and coldest months is recommended.
• Facility type: Warehouses and other large storage areas are more affected by external conditions than smaller, climate-controlled units within a building.
• Previous mapping results: If prior mappings have shown significant temperature differences between summer and winter, seasonal mapping is likely required.
• Regulatory expectations: Some guidelines mandate both summer and winter mappings.
• Timing: Is this the first summer using your facility? Or has it been 3-5 years since the last summer mapping?
• Changes: Have storage conditions changed significantly?

If you can justify that seasonal changes do not impact your storage conditions, you may not need to perform separate mappings; for instance if your TCU operates within a controlled indoor environment with consistent temperature regulation. However, for warehouses and larger storage facilities exposed to external temperature shifts, seasonal mapping is often a requirement.

This year's summer may not be the hottest summer. Mapping during a milder peak means the data does not reflect worst-case conditions. Two ways to manage this:

• Extend the mapping window: Plan a longer study that catches several hot days rather than committing to a fixed five-day window. This builds resilience against a milder-than-usual peak.
• Document the limitation in the report: If positions came close to non-conformance on days that were not the year's hottest, state this clearly. A subsequent climate-driven rise could push those positions out of specification, and the report should reflect that.

Extreme summers have become more common in recent years, and a validation report that acknowledges year-on-year variability is stronger than one that does not.

How should you conduct your summer mapping in GxP?

1. Plan ahead

By planning your summer mappings in advance, you will adhere to compliance standards and ensure the continuous quality of your products during this temperature-critical period. And as a (quite big) bonus - you avoid unnecessary stress and last-minute work. Not to mention, completely missing the season.

2. Determining when to conduct summer mapping

Instead of relying on fixed calendar dates, perform your summer mapping when ambient external temperatures are at their seasonal peak. In some regions, this may occur in early spring or extend into autumn. Checking historical temperature data and monitoring real-time weather patterns can help determine the optimal timing.

3. Accounting for sun and radiation heating

Sunlight and radiation play a significant role in temperature fluctuations within storage facilities.

Consider factors such as:

• Sun-facing walls and windows: These can absorb heat, creating localized hotspots.
• Roof insulation: Poor insulation can result in significant heat buildup.
• Warehouse gates and truck entrances: These areas often experience temperature spikes due to frequent openings and exposure to direct sunlight.

4. Monitoring the impact of outside air temperature

Unlike winter mapping, where external cold air can seep into storage spaces, summer mapping focuses on how external heat affects internal conditions.

Key considerations include:

• HVAC overload: High temps strain cooling systems, risking failures.
• Increased door openings: Frequent use can cause internal temperature fluctuations.
• Cooling energy consumption: Monitoring efficiency is key.
• Thermal stability risks: Weak insulation and sun exposure can create hot spots.
• Humidity control: Higher moisture levels can affect storage conditions.
• Seasonal staffing changes: Ensure personnel are trained for proper monitoring.

5. Evaluating equalization of product temperatures

When products arrive at a facility, their temperatures may differ significantly from the storage environment. In summer, goods arriving from hotter external locations may take longer to stabilize.

This can impact:

• Cooling system efficiency as the HVAC works harder to compensate.
• Storage compliance, particularly if sensitive products are placed in at-risk areas before stabilizing.
• Mapping accuracy, as product temperature variations may skew results.
• Some facilities use intermediate storage zones to allow products to gradually equalize before being placed in final storage.

Also read: How to control temperatures in your cooling equipment during summer

Once seasonal mapping is on the table, the next question is how to sequence it. Three approaches are in use across the industry, each with different operational tradeoffs.

Traditional: separate summer and winter studies

Conduct summer mapping when temperatures peak, take the loggers down, wait six months, then install them again for winter mapping. In the strictest interpretation, full routine operation depends on both seasonal studies being complete, which can delay it by up to six months.

Interim: leave the loggers in place between mappings

Conduct summer mapping, then leave the loggers installed rather than removing them. The facility can enter operation under increased vigilance, and the additional sensors generate continuous data through the intervening months. Conduct the winter mapping when temperatures drop, then transition to normal monitoring. Most regulators accept this approach because the increased data coverage compensates for the staggered seasonal evidence.

Continuous: skip the seasonal mapping as a discrete event

Conduct the initial mapping, then leave a defined percentage of the loggers in place permanently. The facility is mapped year-round, which covers every season and every operational state by default. Seasonal mapping stops being a recurring project, and year-on-year variability is largely managed inside the ongoing dataset. The concept is described in ISPE's Good Practice Guide on controlled temperature chambers as continuous temperature mapping.

Also read: Traditional vs. continuous mapping

A common mistake in seasonal mapping reports is closing with a single conformant or non-conformant statement. Auditors and operations teams both benefit from more detail.

A useful summer mapping report identifies:

• Risk zones rather than single points: The areas of the volume most exposed during summer conditions, and how those areas should be used.
• Areas that should not be used: Even in a small fridge, a single shelf may run consistently warm during summer. Documenting this explicitly is more useful than averaging it into a pass.
• Operational recommendations: How to use the space given what the data shows. Sensitive products in more stable zones, less sensitive items in the marginal zones, and so on.
• Near-misses: If a position came close to the acceptable range on days that were not exceptionally hot, flag this. A small further temperature rise could push it out, and noting this in the report is the responsible position for a validation engineer to take.

Also read: How to build a temperature mapping report

Hot and cold spots can shift between seasons

The hottest spot in summer may not be the hottest spot in winter, and the same applies to cold spots. This has a direct implication for where you place permanent monitoring sensors. If only summer data is available, the monitoring sensors are positioned on incomplete information. Comparing summer and winter mapping data side by side gives the right basis for permanent placement, and where the two seasons identify different extremes, the monitoring strategy should cover both positions.

Regulatory bodies increasingly expect companies to take a risk-based approach to mapping rather than blindly following grid-based placement methods. This means:

• Identifying areas most vulnerable to temperature fluctuations.
• Adjusting mapping strategies based on facility-specific risks (e.g., HVAC configurations, sun exposure, and operational factors).
• Ensuring auditable documentation to demonstrate a proactive approach to compliance.

Also read: Guidelines for risk-based temperature mapping in GxP