United States climate exposure

Seattle Climate Exposure: Maritime Humidity, Chloride and Sulfate Background

Seattle represents a cool maritime environment where persistent wetness, Puget Sound chloride exposure and sulfate background matter more than heat.

Climate exposure summary
CE-3Maritime Wet Exposure
  • Persistent wetness and humidity
  • Strong Puget Sound chloride context
  • Low heat but elevated corrosion relevance

Marine humidity is the primary stressor. Chloride and wetness is the secondary driver for reliability and field durability decisions.

CE classes describe overall environmental severity and are not equivalent to ISO corrosivity classes.

Dominant mechanismsCool maritime wetnessChloride screening exposureSulfate deposition context
Temperate MaritimeHigh humidityStrong coastal / Puget Sound marine exposure
Seattle47.606, -122.332
Engineering Climate Fingerprintâ„¢

Seattle environmental load barcode.

A normalized 0-100 matrix showing which exposure mechanisms dominate the deployment environment. Scores describe environmental load intensity, not failure probability.

ECF patternPrimary: Marine · Secondary: Humidity
Humidity68High
Condensation58Moderate
Thermal34Low
Marine92Severe
Pollution32Low
Freeze16Low
Humidity: Temperate maritime RH80 and cool-season humidityCondensation: Cool humid periods and dew-point marginThermal: Mild seasonal range with limited heat stressMarine: North America V2 total chloride at Seattle: 437 mg/m2/dayPollution: MERRA-2 sulfate deposition background at Seattle: 2.2 mg/m2/dayFreeze: Occasional frost and freeze-thaw relevance
Typical Applications

Equipment categories where this climate profile is relevant.

Outdoor ElectronicsTelecom EquipmentMarine-adjacent InfrastructureEV ChargingIndustrial EquipmentTransport Electronics
Why this climate matters

Why Seattle climate matters

Seattle is a useful engineering reference for cool maritime exposure: corrosion relevance can be high even when heat stress is modest.

The Pacific Northwest atmospheric layer adds calibrated chloride context around Puget Sound, which is not visible from annual average temperature alone.

For qualification planning, Seattle is a contrast case to Houston: both have corrosion relevance, but Seattle is driven by cool wetness and marine chloride rather than hot-humid operation.

Engineering metrics

Exposure metrics that matter before deployment.

Climetry-derived indicators summarize environmental severity. ISO-derived indicators estimate material-related atmospheric corrosivity for metals such as carbon steel, zinc, copper and aluminum.

Climate Exposure SummaryCool maritime exposure

Persistent humidity with strong Puget Sound chloride context.

Corrosion RiskHigh

Pacific Northwest chloride layer indicates strong marine screening exposure at Seattle.

Condensation RiskModerate

Cool humid periods and limited drying potential can support surface wetness.

RH80 Hours4,691 h/year

CEY10 long moisture exposure window for outdoor and semi-outdoor products.

RH90 Hours2,642 h/year

CEY10 high-humidity periods occur mainly in cool wet seasons and nights.

Climate ClassificationTemperate Maritime

Cool seasonal climate with maritime wetness and chloride modifier.

Monthly climate profile

Seattle thermodynamic exposure by month.

Preview profiles show monthly min-max envelopes, P10-P90 percentile bands, and monthly means for the core thermodynamic variables.

Relative humidity

76 % annual mean

Cool-season humidity and wetness dominate the Seattle exposure profile.

46 %75 %104 %JanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Air temperature

11.8 C annual mean

Thermal stress is moderate and seasonal; heat is not the primary reliability driver.

-5.2 C12.3 C29.9 CJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Absolute humidity

8.4 g/m3 annual mean

Absolute humidity is lower than tropical sites but drying potential is limited in wet seasons.

0.0 g/m38.9 g/m317.7 g/m3JanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Dew point

7.1 C annual mean

Dew point remains close enough to air temperature for condensation screening in cool periods.

-5.4 C7.5 C20.4 CJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Hourly CEY engineering statistics

Seattle representative-year diagrams.

These figures are calculated from the local hourly Climetry Environmental Year and translate thermodynamic climate data into engineering-readable duration, cycle and moisture-risk views.

Seattle CEY10 temperature duration

CEY10 temperature duration

Seattle's 1 C temperature-duration histogram is calculated from the selected hourly CEY10 source months. It shows how long products experience each outdoor temperature band during the representative year.

Seattle CEY10 relative humidity duration

CEY10 relative humidity duration

The RH duration histogram translates relative humidity into annual exposure hours. It supports moisture-sensitive electronics, coating, connector and enclosure screening.

Seattle Temperature x RH occurrence

Temperature x RH occurrence

The joint duration heatmap shows which temperature and humidity combinations occur together. This is more useful for durability screening than separate annual averages.

Seattle Psychrometric moisture density

Psychrometric moisture density

The psychrometric density view connects dry-bulb temperature with absolute humidity and helps identify moisture-rich operating conditions and drying limitations.

Seattle P05 / P50 / P95 thermodynamic profile

P05 / P50 / P95 thermodynamic profile

The percentile profile summarizes the representative spread of temperature, dew point, relative humidity, absolute humidity and dew-point margin.

Seattle Representative moisture-risk week

Representative moisture-risk week

The selected high-risk week highlights periods with elevated humidity, absolute humidity and small dew-point spread. It is a screening view for condensation and moisture-ingress relevance.

Seattle Daily temperature cycle histogram

Daily temperature cycle histogram

Daily temperature-cycle statistics provide engineering input for thermomechanical reliability assessments, enclosure breathing and gasket stress screening.

Seattle Heating-design cold-week histogram

Heating-design cold-week histogram

The cold-week temperature histogram is useful for heating-load screening in temperate and cold climates. In tropical climates it confirms low heating-design relevance.

Definitions

Terms used on this page.

CE class

A Climetry Exposure Class is a location-based environmental severity class for durability screening.

CE classes summarize humidity, condensation potential, marine influence, pollution context and thermal exposure. They are not ISO 9223 corrosivity classes.

RH80 exposure

RH80 exposure is the number of hours where relative humidity is at least 80%.

It is useful for identifying persistent moisture exposure relevant to electronics, coatings, connectors, enclosures and atmospheric corrosion screening.

Condensation potential

Condensation potential indicates conditions where surface wetting risk is elevated.

It is derived from temperature, dew point and humidity context. It is a screening indicator, not a measurement on a specific product surface.

Atmospheric transport screening

North America V2 chloride and MERRA-2 sulfate context.

Seattle chloride is sampled from the current Climetry North America V2 land-only total chloride overlay. Sulfur exposure is represented by MERRA-2 sulfate deposition background rather than uncalibrated SOx magnitude.

Annual Grid-Cell Chloride30.9 mg/m2/day

Annual mean sampled at Seattle from the current North America V2 land-only total chloride overlay.

Chloride StatusV2 ISO screening

North America V2 combines NADP-calibrated marine wet deposition, dry-deposition uplift and a coastal aerosol tail. The open-fetch classifier damps sheltered Puget Sound relative to exposed Pacific coastline.

Distance to Coast1.1 km

Seattle's sampled grid cell is immediately marine-influenced in the Puget Sound corridor.

MERRA-2 Sulfate2.2 mg/m2/day

Annual wet+dry sulfate deposition background sampled from MERRA-2.

Sulfate ConfidenceValidated background

MERRA-2 sulfate is used as sulfur-deposition background; local SOx transport remains research/screening context only.

ISO Input ClassesT4 / S1 / sulfate background

Approximate screening inputs: time of wetness, V2 total chloride and MERRA-2 sulfate deposition background.

Carbon SteelScreening only

Cool wetness plus moderate V2 chloride produce a corrosion-screening context.

AluminumScreening only

Chloride-sensitive aluminum interpretation should use the V2 total chloride value and site-specific shielding.

Corrosion DriverWet marine chloride

For Seattle, persistent wetness and Puget Sound chloride context dominate over heat exposure.

Monthly atmospheric transport profile

Seattle chloride and sulfate screening by month.

Monthly chloride values are sampled from the current North America V2 total chloride overlay at the Seattle grid cell. Sulfate values are sampled from MERRA-2 2020-2024 monthly wet+dry deposition background.

Chloride deposition

30.900 mg/m2/day annual mean

Monthly V2 total chloride estimates remain in the S1 screening range. The updated open-fetch model avoids treating sheltered Puget Sound shoreline as exposed surf coast.

25.476 mg/m2/day31.450 mg/m2/day37.424 mg/m2/dayJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
MERRA-2 sulfate deposition

2.239 mg/m2/day annual mean

MERRA-2 sulfate background is low to moderate for Seattle; chloride and wetness remain the stronger corrosion-screening drivers.

0.621 mg/m2/day2.210 mg/m2/day3.799 mg/m2/dayJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Plastic ageing context

Seattle UV and ozone exposure for polymer screening.

Seattle shows strong seasonality. Winter UV exposure is low, while summer reaches high enough levels for polymer photo-oxidation screening.

Mean UV Surface Dose46.0 kJ/m2/day

ERA5 2015-2024 monthly climatology sampled at the city grid cell.

Peak UV Month84.2 kJ/m2/day

Highest monthly mean daily UV dose in the representative climatology.

Mean Surface Ozone27.5 ppb

CAMS EAC4 surface ozone climatology for elastomer and rubber ageing context.

Plastic Ageing Index65 / 100

Partial Climetry v0.1 screening index from UV and ozone only; not a lifetime prediction.

Engineering interpretation

Plastic ageing in Seattle is seasonally concentrated rather than year-round severe. For outdoor enclosures, the polymer story should be combined with cool wetness, chloride and limited drying potential.

Monthly plastic ageing profile

Seattle UV and ozone exposure by month.

Monthly profiles show UV surface dose, surface ozone and a partial Plastic Ageing Exposure Index. Thermal oxidation, hydrolysis and moisture ageing will be refined with CEY thermodynamic channels.

UV surface dose

46.0 kJ/m2/day annual mean

Mean daily UV surface dose by calendar month. Useful for photo-oxidation screening of plastics, coatings, cable jackets and exposed polymer housings.

0.0 kJ/m2/day49.7 kJ/m2/day99.4 kJ/m2/dayJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Surface ozone

27.5 ppb annual mean

Monthly surface ozone climatology. Relevant for ozone-sensitive elastomers, seals, rubber parts and strained polymer components.

7.5 ppb26.7 ppb45.8 ppbJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Plastic ageing exposure

65 score annual mean

Partial Climetry Plastic Ageing Exposure Index v0.1 from UV and ozone channels only. Thermal and moisture ageing channels will be added from CEY.

12 score54 score97 scoreJanFebMarAprMayJunJulAugSepOctNovDec
Min-max P10-P90 Mean
Environmental Data Confidence

ERA5 climate data show consistent long-term environmental agreement.

The environmental indicators presented on this page are derived from ERA5 climate data.

ERA5 thermodynamic variables have been compared against long-term airport weather station observations across multiple climate regions.

The comparison demonstrates good agreement between ERA5 and measured environmental conditions.

TemperatureRMSE 1.15 °C
Dew pointRMSE 1.20 °C
Relative humidityRMSE 5.48 %-points

These comparisons evaluate long-term environmental representativeness and not individual weather events.

Local Station Consistency

Seattle: ERA5 vs Weather Station Observations

Monthly thermodynamic comparison against Seattle-Tacoma International Airport (KSEA) weather observations for 2025.

TemperatureRepresentative maritime profile
Dew pointCool-wet context
Relative humidityScreening comparison pending
Meteostat monthly valuesERA5 monthly values
City-specific comparison against Seattle-Tacoma International Airport (KSEA). The chart is schematic; the RMSE values above are calculated from monthly station-versus-ERA5 2025 data.Read methodology
Report preview

Seattle exposure report structure.

The full report combines climate classification, corrosion screening, condensation exposure, RH80/RH90 hours, marine context, monthly profiles, and reliability implications.

Climate ClassificationTemperate MaritimeClimate zone
Climetry Exposure Class (CE)CE-3Environmental severity
Corrosion ScreeningHighISO-derived indicator
Condensation RiskModerateMoisture
RH80 Hours4,691 h/yearWet-hour proxy
RH90 Hours2,642 h/yearExtreme humidity

Reliability implications for Seattle

High humidity and condensation exposure may result in a severe Climetry Exposure Class even if atmospheric metal corrosivity remains moderate. CE classes indicate environmental severity and qualification relevance, not failure probability.

  • Treat wetness duration, marine humidity and chloride screening exposure as central assumptions for outdoor assets.
  • Review coating systems, connector sealing, drainage and exposed fastener choices for maritime deployments.
  • Use Seattle as a cool-wet contrast to hot-humid Gulf Coast environments such as Houston.
Learn More

Engineering context behind the city exposure pages.

Interactive assessment

Understand your own environmental exposure.

Analyze any location worldwide and compare humidity, condensation and environmental severity.

FAQ

Frequently asked questions

What does CE-3 mean for Seattle?

CE-3 is a Climetry Exposure Class. It describes overall environmental severity for durability screening and qualification support at this location.

Is this a corrosion prediction?

No. The page provides environmental exposure screening. Corrosion indicators are engineering screening outputs, not failure probability and not a product-specific lifetime prediction.

How reliable are the climate data?

The indicators are derived from ERA5 climate data. ERA5 thermodynamic variables have been compared against representative airport weather observations and show good monthly agreement for temperature, dew point and relative humidity.

What is the difference between CE class and ISO corrosivity?

CE classes describe overall environmental severity. ISO 9223 corrosivity classes describe material-related atmospheric corrosivity categories. They are related but not equivalent.

How does Climetry use ERA5?

Climetry uses ERA5 temperature, dew point and pressure fields to derive relative humidity, absolute humidity and environmental exposure indicators for engineering interpretation.