Lesson Plan

Freeing the Elwha (Weather Patterns of the Pacific Coast)

A winter view of the Olympic Mountains.


How can learning about weather patterns help us to understand our water resources?


The weather in the Pacific Northwest is dependent on the Pacific Ocean. Generally speaking, weather in the region is mild, with cool wet winters, and warm dry summers with extremes in temperature and precipitation being unusual. However, despite the moderating effects of the Pacific Ocean, the mountains are very important in terms of the distribution of precipitation across the region and the development of water storage in the form of a snowpack during the summer drought. The mountain, via topographical lifting and the rainshadow effect, causes some areas to be temperate rainforests, while others become deserts.

  • Condensation: The transition of water vapor into liquid
  • Dew point: The temperature at which relative humidity reaches 100% and liquid water condenses from the air.
  • Rainshadow Effect: As clouds pass over the mountains, they drop precipitation on the windward side. But, when the air drops on the leeward side, it warms up, causing the clouds to evaporate again into vapor due to the temperature rising above the dew point temperature. This adiabatic heating and cloud evaporation results in drier conditions on the leeward side of the mountains
  • Adiabatic Heating: The compression and heating of air as it descends from high elevation to low elevation
  • Snowpack: The seasonal accumulation of snow in the winter that is available for melting in the spring and summer.
  • Glacier: A body of compacted ice that flows due to gravity under the weight of the ice above.


  • Lesson 1- Precipitation Patterns of the Pacific Coast.pptx
  • Lesson 1a- Precipitation Patterns of the Pacific Coast.pdf
  • Glass jar with top
  • Ice bath or refrigerator/freezer
  • Heater or hot water in a pitcher
  • Reflection journal Pages (Printable Handout)
  • Vocabulary Notes (Printable Handout)



Go over the essential question, introduce the guiding question.

Have students take a few minutes to respond to the reflection journal prompt. Discuss responses then questions they may have.

Hand out and go over the vocabulary notes. Have students define vocabulary words as they watch the PowerPoint Lesson. Some words may need to be defined elsewhere.

Present the PowerPoint Lesson

Discuss the concepts of dew point, topographical lifting, condensation, and the formation of clouds and precipitation.

Run Demonstration on Condensation

Discuss the seasonal precipitation patterns of the Pacific Northwest and the concept of the Rainshadow Effect, which results in heavy precipitation on the windward slopes facing the ocean and drier conditions on the leeward slopes.

Discuss snowpack and the formation of glaciers.

Finally have students respond to the second reflection journal page.

Park Connections

Precipitation/Climatic Patterns in the Northwest, the Rainshadow Effect, Snowpack and Glaciers

Additional Resources






Rain shadow animations and tutorials:



Dew point
Rainshadow Effect
Adiabatic Heating