Summer (June through September) is by far the best time to visit Forest Grove. Temperatures sit in the mid-20s C (around 75 to 85 F), the rain almost stops, and the surrounding farmland and wineries are at their busiest and most photogenic. July and August are the warmest months.
Spring is wet but green and pretty -- ideal for the small-town walks and cycling around Henry Hagg Lake before the summer crowds. Autumn brings the wine harvest, vineyard tours, and the Forest Grove Concours d'Elegance car show in July. Winter is cool, grey, and damp; the wineries are quieter but tasting rooms remain open, and Pacific University holds its varsity sports indoors.