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.
From Portland drive to the East to North Bonneville (Washington) or Bonneville (Oregon). The best access is not know exactly. Try to find it from the Oregon side and Washington side to find the best launch in that area. Supposely the Washington side has the better launch and riding. Find it.