Can’t comment on the weather but I just finished riding from Portland to SF the first two weeks of September. My average mileage was 53 miles per day. I rode a total of 636 miles. There was a fire near Brookings (Chetko Bar Fire) which produced a lot of smoke. My son convinced me to skip about 200 miles south to miss all the smoke so I did not ride from Port Orford, OR to Ferndale, CA. My days were as follows:

Hillsboro to Tillamook – 63 miles / 5.4 hr riding time (not including any stops)
Tillamook to Beverly Beach SP – 77 miles / 7.3 hrs riding
Beverly Beach SP to Jesse Honeyman SP – 63 miles / 5.8 hrs riding
Jesse Honeyman SP to Sunset Bay SP – 57 miles / 5.5 hrs riding
Sunset Bay SP to Humbug Mtn SP – 61 miles / 6.1 hrs riding
(Drove from Humbug Mtn SP to Ferndale)
Ferndale to Burlington CG (Weott) 35 miles / 3.3 hrs riding
Burlington CG to Standish Hickey SP – 48 miles / 5.3 hrs riding
Standish Hickey SP to Fort Bragg – 46 miles / 5.4 hrs riding
Day off in Fort Bragg
Fort Bragg to Gualala County Park – 63 miles / 5.8 hrs riding
Gualala to Bodega Dunes SP – 50 miles / 4.9 hrs riding
Bodega Dunes to Samuel Taylor SP – 44 miles / 4.3 hrs riding
Samuel Taylor SP to south side of Golden Gate Bridge 29 miles / 2.9 hrs riding

Regarding riding times, I am 65 and overweight so only averaged around 10 mph. BTW if you go, Manchester SP in CA is closed but the KOA nearby offers hiker/biker rates.