September 2013 Climate Summary for northern and eastern Maine

September 2013 will be remembered mostly for the continuation of the inclement and very wet weather trend across northern and eastern Maine which began this past mid-may. Most locations experienced temperatures which averaged close to 1 degree above average from the 1981-2010 September mean normal temperatures, with individual locations ranging from near normal to upwards of 2 degrees above average. Typical of a fall (or spring) transition month, there was no steady trend of above or below normal temperatures, but rather an alternation of 2 to 4 day periods of each. Most locations experienced their warmest day on the 11^th which featured highs in the low to mid 80s north of the immediate coast and south of the Saint John Valley. This was followed within 6 days by the coolest morning on the 17^th, where many locations reported lows in the 30s with some frost, and even some below freezing low temperatures as evident by the low of 28 degrees at Houlton.

Although rainfall for the region as a whole was much above normal, there was considerable location to location variation, indicating that repeated localized heavy downpour events played more of a role for some locations than others this month. For instance, at Caribou and Bangor, which had their 3rd and 4th wettest September of record respectfully, monthly rainfall totaled about 210 percent of normal, while other locations such as Frenchville and Millinocket experienced only about 110 to 120 percent of normal September rainfall. The average percentage rainfall for the month and region as a whole was likely between 150-175 percent. Significant to major rain days affected some portion of the region on the 1^st, 2^nd, 11th-13^th, and the 22^nd, with many other lesser rainfall days accompanied by cloudy conditions. With the addition of heavy rainfall this month, a few locations such as Orient in southeast Aroostook County...have totaled close to 40 inches since May 1st of this year, which is more than what typically falls in a calendar year in just a four month period!

The official regional outlook for October from the Climate Prediction Center (CPC) is calling for greater chances of above normal temperatures rather than near normal or below normal temperatures, and equal chances of either above, near normal or below normal precipitation. With little or no forcing from El-Nino or La-Nina expected this coming month, the tool driving CPC`s outlook the most for our region is persistence of past Octobers over the last 10 to 15 years.