weather in vernonia, oregon fahrenheit
Oregon Weather > Vernonia Weather. Vernonia, OR climate is mild during summer when temperatures tend to be in the 60's and very cold during winter when temperatures tend to be in the 30's. The warmest month of the year is August with an average maximum temperature of 76.50 degrees Fahrenheit, while the coldest month of the year is January with an average minimum temperature of 29.10 degrees Fahrenheit.