By Rod Hill on 2011-02-09
Climate data continues to show an adjustment in seasons. The western and northern United States are leading the country in the expansion of the growing season. (The growing season is the period usually from spring to fall with no freezing temperatures.) Here in the Northwest, the growing season has grown 14-20 days over the past 20 years. Perhaps more impressive here at home is a trend toward an earlier final spring freeze.
The 30-year climate average for Portland says the average last spring freeze is March 30th. Colder areas such as Salem and Hillsboro average a final freeze closer to April 30th. If you look at the records for PDX dating back to the year 2000, the average final freeze is March 16th. If the trend holds, the average last spring freeze will occur two weeks earlier than past years! Of course, I am talking averages only. Some years will likely continue to see freezes all the way towards May 1st.
Also of interest to me, is the fact that the last 10 plus years have seen no large winter storms past the middle of January. Remember the last 10 Februarys here in Portland, have all been below normal in terms of precipitation. Lots of data supports a 10 year trend of harsh winter weather ending earlier than past decades.
No matter where you look, climate shift or change seems to be happening. No matter what the reason, this is an interesting time.
Weather change this coming weekend