What is a Climetry Exposure Class?
A Climetry Exposure Class, or CE class, is a location-based environmental severity category from CE-1 to CE-5. It exists for one practical reason: a design review or deployment decision rarely works with dozens of climate statistics, but it can work with a statement such as "this site is CE-4" backed by the numbers behind it.
The class is relative. It does not say that a climate exceeds a physical damage threshold; it says how the location ranks against Climetry's global benchmark of gridpoints. That makes it useful for comparing candidate sites and for deciding where qualification needs a closer look, and it is also why the class must not be read as a corrosion rate or a failure probability.
How the class is assigned
In the Point Analysis, three indicators are calculated from the site's hourly CEY10 representative year (2015-2024) and each is ranked as a percentile against all benchmark gridpoints:
Hour-weighted mean relative humidity of the site's representative year.
Share of hours in which air temperature is within 2 C of the dew point.
Climetry screening value derived from ISO 9223 dose-response rates for carbon steel and aluminium (temperature, humidity, chloride and SO2 inputs). Each rate is divided by a fixed reference rate and multiplied by 100, and the higher of the two is used. The indicator has no upper limit and can exceed 100; only its percentile rank runs from 0 to 100. It is not an ISO corrosivity category.
The class follows the highest of the three percentiles:
| Class | Highest percentile | Label in the report |
|---|---|---|
| CE-5 | 95th or higher | Severe comparative climate exposure |
| CE-4 | 80th to below 95th | Harsh comparative climate exposure |
| CE-3 | 60th to below 80th | Elevated comparative climate exposure |
| CE-2 | 40th to below 60th | Moderate comparative climate exposure |
| CE-1 | below 40th | Benign comparative climate exposure |
Taking the maximum is a screening choice: one extreme dimension is enough to flag a site. The report's fingerprint pages show separate land-only percentiles for humidity, condensation and temperature; those are context and do not change the CE class.
Worked example: the Stuttgart demo report
The public demo Point Report for Stuttgart is a historical report (Point Report v1.2, generated 2026-09-05, CEY10 representative year 2015-2024). It contains every value needed to follow the rule, and all numbers below are taken from that PDF. The example explains how the class is assigned; it is not a validated finding about Stuttgart's corrosivity.
| Coordinate | 48.7758 N, 9.1829 E (Stuttgart) |
| Data basis | CEY10 representative year 2015-2024, Point Report v1.2 generated 2026-09-05 |
| RH >= 80 % | 4,327 h/year |
| Condensation-potential hours | 2,724 h/year |
| Percentile rank of the corrosion indicator across all benchmark gridpoints | 100th |
| Resulting CE class | CE-5 (highest percentile >= 95) |
| ISO-derived carbon steel corrosivity | 19.2 um/year, C2 (chloride 0.6 mg/m2/day, ISO salinity S0) |
The corrosion indicator has the highest of the three percentile ranks, so it decides the class: a rank of 100 is above 95, which gives CE-5. In the same report the ISO 9223-derived rate for carbon steel is 19.2 um/year, category C2, because chloride is low (S0) and the ISO functions respond strongly to chloride. The two results answer different questions, and neither says how long a product will last.
The global benchmark computes the corrosion indicator from each gridpoint's annual mean temperature and humidity, while the site value is an hour-weighted aggregate of monthly indicators. Because the ISO dose-response functions are non-linear, the two methods are not strictly equivalent, so the site's percentile rank may differ from the rank it would get under one consistent method. The direction and size of that difference, and whether it affects this example, have not been determined. Until both are computed the same way and the ranks are re-validated, read this example as a demonstration of how the rule works, not as evidence that Stuttgart is among the most corrosive places in the world.
Environmental severity, ISO corrosivity and failure probability
Three different questions are often merged into one word, "harsh". Keeping them apart avoids most misreadings of a CE class.
| Concept | How it is obtained | What it describes | What it does not tell you |
|---|---|---|---|
| Climetry Exposure Class (CE) | How the site's climate ranks against Climetry's global benchmark gridpoints. | Environmental severity relative to other places | Not a material class and not a failure probability. |
| ISO 9223 corrosivity category (C1 to CX) | Estimated first-year corrosion rate of a specific metal from the ISO 9223 dose-response functions. | Material-related atmospheric corrosivity | Says nothing about electronics, polymers or condensation inside enclosures. |
| Product failure probability | Requires the product's design, materials, failure mechanisms and field or test evidence. | Reliability of a specific product | Neither CE nor ISO classes provide it. |
High humidity and condensation exposure may result in a severe Climetry Exposure Class even if atmospheric metal corrosivity remains moderate.
Engineering consequences
The Point Report attaches qualification guidance to the class and to the individual percentiles:
- Every class: use the monthly profile to pick representative hot-humid and condensation-prone test conditions, and confirm enclosure, coating, connector and drainage performance with product-specific acceptance criteria.
- CE-4 and CE-5: add combined temperature-humidity cycling and powered condensation testing before deployment.
- Corrosion percentile of 80 or higher: add corrosion-focused material and coating tests, and replace screening chloride and pollution assumptions with measured site deposition data where available.
- In all cases: map final test severities to the applicable IEC, ISO, customer or internal qualification standard.
City examples
The city pages show a CE class for each example location. Those classes were assigned with an earlier version of the screening and have not been recomputed with the Point Analysis rule above, so treat them as orientation and open each page for its underlying data.
Class as stated on the city page.
CE-3 · Cool maritimeSeattleClass as stated on the city page.
CE-3 · Temperate maritimeLondonClass as stated on the city page.
CE-4 · Humid subtropicalHoustonClass as stated on the city page.
CE-4 · Cool marineSan FranciscoClass as stated on the city page.
CE-4 · Hot arid coastalDubaiClass as stated on the city page.
CE-5 · Humid tropicalSingaporeClass as stated on the city page.
CE-5 · Tropical monsoon coastMumbaiClass as stated on the city page.
Limitations
A CE-5 classification is not a failure probability. A CE-5 site does not mean a product will fail, and a CE-2 site does not guarantee long-term durability. Product design, material selection, coatings, maintenance, manufacturing quality and qualification testing still matter.
The class is relative to Climetry's benchmark. The CE ranking uses all benchmark gridpoints, including ocean gridpoints; the land-only percentiles in the report fingerprint are shown separately. A change in the benchmark population changes the ranks, even if the site's climate does not.
RH80, RH90, condensation hours, corrosion and plastic ageing metrics.
ProductAnalyze any location with Climetry exposure metrics.
Scientific validationHow the ERA5-Land climate basis compares with independent weather stations, and what that check does not cover.
Engineering hubRelated articles on corrosion, humidity, UV, representative years, heat pumps and solar.
See the class and the numbers behind it.
The Point Analysis reports the CE class together with the percentiles, humidity hours, condensation and ISO-derived corrosivity it is based on.
Frequently asked questions
What is a Climetry Exposure Class?
A Climetry Exposure Class is a CE-1 to CE-5 environmental severity category for durability screening. In the Point Analysis it is set by the highest of three global percentile ranks: humidity, condensation and a corrosion indicator.
How is the CE class calculated?
The site's representative-year humidity, condensation share and corrosion indicator are ranked against Climetry's global benchmark gridpoints. The highest of the three percentiles decides the class: 95th or higher is CE-5, 80th to 95th CE-4, 60th to 80th CE-3, 40th to 60th CE-2 and below 40th CE-1.
Is CE-5 the same as ISO C5?
No. CE classes are not ISO 9223 C classes. CE ranks a site's climate against other places; ISO C classes estimate the atmospheric corrosivity for a specific metal. A site can be CE-5 and still screen as ISO C2 for carbon steel.
Does CE-5 mean a product will fail?
No. CE classes indicate environmental severity and qualification relevance, not failure probability.
Why can one dimension push a site into CE-5?
Because the class follows the highest of the three percentiles. This is deliberate for screening: a single extreme exposure dimension is enough to justify a closer look during qualification planning.