to the coast and Portland. The region's climate is similar to the Central and Sacramento Valleys of California, with a hot-summer Mediterranean climate. Winters are chilly and rainy, but relatively dry and slightly colder when compared to the rest of western Oregon, with frequent fog, and occasional snow. Summers are hot and sunny, but dry, with low or no humidity. Temperatures surpass , on an average of 10–15 days during the summer. Because of the combination of heat and dry air, wildfires are a problem during the summer, and frequently, smoke will fill up the valley for weeks, reducing visibility and air quality. On average, the first frost occurs October 22, and the last on May 6. The Rogue Valley is in USDA plant hardiness zones 7–9. Sub-zero temperatures are extremely rare in the valley; the Rogue Valley International-Medford Airport has not recorded such extreme cold weather since December 21, 1990, when the temperature dropped to . Due to the valley's generally mild climate, it is used as a region to grow pears, and there are multiple vineyards. Medford has, on average, 175 sunny days per year, compared to 80 on average for the Willamette Valley, and 65 on average for the coast. See also Jefferson (Pacific state) Roxy Ann Peak Upper and Lower Table Rock Psathyrella aquatica References Valleys of Oregon Rogue River (Oregon) Regions of Oregon Landforms of Jackson County, Oregon Landforms of Josephine County, Oregon Klamath Mountains Cascade Range