Buy the 2015 Old Farmer's Almanac!
Unfortunately at the moment,Unfortunately at the moment, because of the government shutdown, the NCDC (National Climatic Data Center) Web site, with weather records, is not accessible for you to find the official information. However, we've found some non-government sources that might help.   The dates will depend on what temperature data you are using (32 degrees, 36 degrees), and what percentile of occurrences (10, 50, 90 percent, etc.). We use 32 degrees and 50 percent. From what we're finding from non-government sources, the last expected spring frost for Astoria can average around April 8 or 9 (for other temps/percentages, it can be as early as mid-March, more mid-April, or April 30 or May 1), and the first expected fall frost around November 7 to 9 (for other temps/percentages, it can be as early as October 14 or thereabouts, or into early December).   You might also be interested in the following Web site:

Shop Wind Bells in the Almanac General Store