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Northeast Regional Climate Center |
This September was the warmest in the Northeast since 1961. The average temperature for the region was 64.0 degrees, which is 3.8 degrees above normal. All 12 states were above normal, and only Delaware, Maryland, and New Jersey had temperature departures of less than 3.0 degrees. The northern states were the warmest relative to their own state averages. Maine and New Hampshire at 59.2 and 61.8 degrees were both more than 4 degrees above normal. New York and Vermont were 4.5 and 4.0 degrees above normal, respectively. For New Hampshire this September was the second warmest on record, though this month fell more than two degrees short of reaching that record. Overall for the Northeast this was the sixth warmest September on record.
The Northeast received 4.33 inches of rainfall this September, which is 109% of the normal amount. Only New Jersey was under its normal on the month, but only by a 1/4 of an inch. The rest of the region was above normal, and three states were more than an inch above normal. Delaware was the only state more than two inches from the region average. Delaware totaled 7.00 inches on the month which is 2.81 inches above its normal. The other two states over an inch from the average were Rhode Island and Vermont, both received more than 5 inches fo rain on the month. This was the first September with above average precipitation in the Northeast since 1999.
It should come as no surprise that 1999 was the last year with a rainy September, if you can remember names like Dennis and Floyd - tropical systems which dropped torrents of rain on the Northeast. Generally every few years the region sees significant rainfalls from the remnants of such storms. The past couple years have produced a real lack of tropical rains in this transitional month so we were due for a couple hits. Widespread rainfall from the remnants of tropical storm Hanna and hurricane Isidore helped to make up for a dry July and August.
Hanna dropped about an inch of rain over much of the Northeast on September 15th and 16th as it swept north up the Appalachain mountains. The system which had been down-graded to a sub-tropical low was carried out to sea on the 16th by a cold air mass moving in from the northwest. The same air mass also helped squeeze some more tropical moisture out of the sky by assisting in the formation of thunderstorms in NY and NE (thus the higher rainfall totals in those areas). Map of precipitation associated with Hanna.
By the 26th of September when former hurricane Isidore began affecting the Northeast, it was no longer threatening strong winds as it had in the Gulf of Mexico but torrential rains. All major stations along the eastern seaboard reported moderate to heavy rain as the storm made it's way north. During the day on the 27th and 28th Isidore dropped half a month's worth of rain in many locations before finally being whipped up into the Canadian Maritimes by the jet stream. Map of precipitation associated with Isidore.
Monthly Summary of State Temperature and Precipitation Averages.
