You have to launch from the Hood River Sandbar. Then go upwind and aim for the bridge on the north side of the Columbia River. No direct launch or landing possible there.
Weather in the summer can be 90+°F with water temperatures warm enough for boardshorts only in July and August. Shorties come in for June and September. Full wetsuits the rest of the year. Winters are not really kite-able here, with the bitter, blustering Easterly winds bringing snow, hail, and rain.
Spring: March to May, light winds 12-20, somewhat finicky. Summer: June to early September, windy, 15-35, pretty solid. Fall: September to October, light to moderate winds, but very steady: 13-25. The wind is usually gusty. Main direction westerlies. Works in SW, W and NW. With the right wind direction the wind is nice and steady with good strenght.
From Portland get to Hood River. In Hood River get to the sand bar in Columbia River and launch from there. Then you need to go upwind to the north of the river to the bridge over the White Salmon River.
If you can't relaunch or something happens and you need to swim back it can be quiet dangerous. If you can't ride home, swim towards the abandoned dock about 100 yards upwind of the bridge, walk up and over the railroad tracks and hitch a ride to Hood River.