Southern Oregon will move through nearly every stage of early September weather during the coming week, beginning with showers and thunderstorms Sunday before sunshine returns and temperatures climb rapidly across the Rogue Valley. By the middle of the week, portions of Jackson and Josephine counties could approach the mid-90s before another change brings cooler conditions by Friday and Saturday.
The changing pattern will also affect travelers crossing Southern Oregon, particularly motorists using Interstate 5, Highway 199, Highway 140, Highway 62 and routes through the Cascades. Conditions will vary considerably between the valleys, mountain passes, coast and higher terrain during the first part of the week.
Sunday, September 6, begins as the most unsettled day of the forecast period. Showers are expected across portions of Southern Oregon, with thunderstorms possible after late morning. Medford is forecast to reach approximately 69 degrees, while Grants Pass should remain near 70. Ashland could see thunderstorms with temperatures in the mid-60s.
The greatest concentration of showers and thunderstorms is expected over the Southern Oregon Cascades and areas east of the mountains, including portions of Klamath County. Crater Lake, Howard Prairie, Chemult and Chiloquin carry considerably greater precipitation chances than communities farther west.
Travelers should account for rapidly changing conditions Sunday, particularly across mountain highways. Thunderstorms can produce brief heavy rainfall, reduced visibility and lightning even when surrounding areas remain dry. Interstate 5 motorists crossing Sexton Summit and Canyon Creek Pass could encounter showers and isolated thunderstorms. Temperatures at the passes will remain substantially cooler than those in the Rogue Valley.
Sunday night brings the beginning of a transition. Showers diminish across western valleys, skies gradually clear and temperatures fall into the upper 40s and lower 50s. Patchy fog could develop around some Interstate 5 mountain passes overnight and early Monday.
Monday, September 7, brings a much quieter weather pattern. Sunshine returns across Grants Pass, Medford and Ashland, with Grants Pass reaching approximately 77 degrees, Medford near 76 and Ashland around 72. Klamath Falls should remain cooler, reaching the mid-60s. Travelers heading toward the coast will find similarly favorable conditions, although coastal temperatures will remain considerably lower than inland readings.
Tuesday marks the beginning of a significant warming trend. Grants Pass is forecast near 85 degrees, Medford near 84 and Ashland around 82. Klamath Falls should reach the mid-70s. Sunshine will dominate most of the region, with little precipitation expected.
The warmer weather will make Tuesday favorable for highway travel throughout much of Southern Oregon, although the rapid return of dry conditions will also begin drying vegetation following Sunday’s precipitation. September remains part of Southern Oregon’s fire season, and several days of sunshine and rising temperatures can quickly change conditions across grasslands, forests and roadside vegetation.
Wednesday brings the week’s strongest warming. Grants Pass could reach approximately 96 degrees, while Medford climbs into the lower to mid-90s. Ashland is forecast around 90 degrees, Roseburg near 90 and Klamath Falls around 79. Even higher elevations will become noticeably warmer, with Crater Lake expected to reach the 60s.
For motorists traveling Interstate 5 between Grants Pass, Medford and Ashland, Wednesday afternoon will bring hot pavement and substantial temperature differences between valley floors and mountain elevations. People traveling long distances should be prepared for the heat, particularly if carrying children, older adults or animals.
Thursday continues the hot and dry pattern. Grants Pass is forecast in the lower 90s, Medford around 90 and Ashland in the upper 80s. Overnight temperatures Wednesday into Thursday will also be considerably warmer than those experienced at the beginning of the week, with Rogue Valley communities remaining near 60 degrees.
Conditions along the Southern Oregon coast will remain much milder. Brookings is expected to stay in the lower 70s during the middle of the week, while North Bend reaches the 70s. Travelers leaving the Rogue Valley for the coast could therefore experience temperature differences approaching 20 degrees or more.
Friday introduces another substantial change. Temperatures are forecast to retreat into the lower 80s around Grants Pass and Medford, with Ashland dropping into the upper 70s. A slight chance of precipitation returns to portions of the region as clouds increase. Forecast confidence regarding the exact timing and extent of late-week precipitation remains lower than for the earlier portion of the week.
Saturday continues the cooling trend. Grants Pass is expected to reach the mid-70s, with Medford around the upper 70s and Ashland in the lower to mid-70s. Klamath Falls should remain in the upper 60s. Partly cloudy conditions are expected across much of western Southern Oregon, with limited precipitation chances remaining in portions of the region.
The week ultimately divides into three distinct weather periods across Southern Oregon: unsettled and occasionally stormy conditions Sunday, rapidly warming sunshine from Monday through Thursday, and a cooler pattern returning Friday into Saturday.
For residents and travelers, the largest weather contrasts will occur between Sunday’s thunderstorms and the heat developing several days later. Mountain travelers should remain attentive to changing visibility and road conditions Sunday, while those traveling through the Rogue Valley during the middle of the week should prepare for afternoon temperatures reaching well into the 90s.
The return of cooler weather toward next weekend should bring more typical September temperatures to much of Southern Oregon, closing a week that begins with rain and thunderstorms, climbs rapidly toward midsummer heat, and finishes considerably cooler across the valleys, mountains and major travel corridors.