If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Tillamook: The hottest months are usually August and July, with an average temperature of 15°C, while the coldest months are February and December, with an average of 6°C. The rainiest months in Tillamook are December, November, January and March, with each month seeing an average of 258 mm of rainfall.