Castle Rock (WA) Temperature by Month

The average annual maximum temperature in Castle Rock, Washington State, United States of America is 16°C (61°F), with daytime highs ranging from 7°C (45°F) in December to 26°C (79°F) in August. This page covers monthly averages, day-night differences, and how Castle Rock compares to cities worldwide.

In Castle Rock, temperatures can shift dramatically between warm in summer and cold in winter. Nights follow the same pattern, with lows ranging from 12°C (54°F) in August to 1°C (34°F) in December.

The chart below illustrates the average maximum day and minimum night temperatures in Castle Rock by month:

The minimum temperature is often recorded between 4 AM and 6 AM, while the highest temperature is usually reached at 3 PM, when the sun's heating effect is strongest. August, the warmest month, gets 299 hours of sunshine.

The chart below shows the average temperature throughout the year:

Castle Rock's average annual maximum temperature is 16°C (61°F). To put that in context, here's how it compares to a few well-known destinations:

Athens, Greece sits at 23°C (73°F) on average, with hot dry summers and mild winters characteristic of the Mediterranean.

Reykjavík, Iceland averages 9°C (48°F) a year, mild summers by Icelandic standards, but cold winters and frequent wind.

Boston, USA averages 16°C (61°F) annually, with four distinct seasons and cold winters that rival northern Europe.

Brisbane, Australia averages 26°C (79°F) a year, with warm winters and hot, humid summers.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

For cities and regions with significant elevation, altitude is one of the biggest factors shaping local temperatures. As a rule of thumb, temperatures fall by around 6°C for every 1,000 metres gained, so a city at 2,000 metres will typically be around 12°C cooler than a city at sea level in the same region. Higher ground also tends to see more dramatic day-to-night temperature swings, since thinner air loses heat faster after sunset.

For more on Castle Rock's weather, including monthly rainfall, sunshine hours, and humidity, visit our Castle Rock climate page.