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UAF Geophysical Institute

Aside from a few scattered locations across the state, the weather was warmer than normal for September by a margin of about one-half to two degrees Fahrenheit. Temperatures began to shift downward throughout the month, however, as is normally the case with the noticeable decline in day length at that time of year. In fact, the autumnal equinox — the time of equal daylight and darkness around the earth — occurred Sept. 22. Along with the relative warmth came a mix of precipitation conditions – dry in the Interior and north, and wet along the southwest, southcentral, and northern portions of the Panhandle.

The month of September ushered in the first frost at the Fairbanks International Airport weather observing station and the first measurable snow of the 2008-2009 season. Temperatures averaged 46.6 degrees Fahrenheit for the month, which is 2.1 degrees above normal for September. Nighttime low temperatures averaged about 38 degrees, while daytime highs were 56 degrees. The low for the month was 20 degrees Fahrenheit and occurred on Sept. 29. However, the first time the temperature dipped to the freezing point was on the 21st. On September 2 and 7, the high for the month of 71 degrees Fahrenheit was observed. Precipitation totaled 0.64 inches (water equivalent), which is a little more than half the normal amount. At the end of the month, there were a couple of days with snow and the monthly total was 1.8 inches. This amount of snow was a little less than normal for September. Winds at the airport were relatively light, averaging 3.7 mph for the month. On Sept. 29, a high wind gust of 18 mph was observed. Heating degree-days were about 70 units less than average at 544, indicative of the overall warmer month

Big Delta was slightly cooler than normal this September, and was also on the dry side. The mean temperature for the month of 44.4 degrees Fahrenheit is almost a degree below average, with high and low temperatures averaging 53 degrees and 37 degrees, respectively. On Sept. 1, the high temperature reached 67 degrees Fahrenheit and on the Sept. 29, the low for the month was observed, a chilly 16 degrees Fahrenheit. Heating degree-days were just below 590 units for the month. Precipitation was a light 0.27 inches, which is three quarters of an inch less than normal for September. The rainfall events were light as no daily total was more than a quarter inch.

In Anchorage, low temperatures in September averaged one degree warmer than normal at 42 degrees Fahrenheit. High temperatures averaged one degree cooler than normal at 54 degrees Fahrenheit. This made for an average monthly temperature of 48.2 degrees – a value equal to climatology, or the 30-year average. The high temperature hit 60 degrees on the 1st, 2nd, 4th, 5th, and 18th. The low for the month, 28 degrees, was reported on Sept. 29. Heating degree-days totaled 493 units, just below the average 505 units for September. Precipitation was three-tenths-of-an-inch above average at 3.22 inches, all of which came in the liquid form as no snowfall occurred. The greatest one-day-total rainfall was 1.04 inches on Sept. 16, setting a new daily record for that date. Winds at the Ted Stevens Anchorage International Airport averaged 5.6 mph for the month.

Temperatures in Barrow this September averaged nearly three degrees above normal for a monthly mean of 34.1 degrees Fahrenheit. The strongest temperature departures came during the latter half of the month and the high reached 40 degrees Fahrenheit on Sept. 19. The low for the month, 22 degrees, occurred on Sept. 29, though temperatures predominantly stayed in the 30s until the last week. Measurable snowfall occurred on four days during the last week of September for a monthly total of six-tenths-of-an-inch. There were a few days with rain around the 10th and these meager totals, plus the water equivalent of the snow events, made for a total of seven-hundredths-of-an-inch of total precipitation. This was only 10 percent of normal for September. Heating degree-days totaled 1,016 units, which is 100 fewer than normal.

Warm and dry conditions greeted Nome this September, with the source of the warmth coming mostly from well above normal afternoon highs. In fact, the average high temperature for the month was a relatively balmy 53 degrees Fahrenheit, which was a positive departure of four degrees. Nighttime lows were close to average, and were around 38 degrees Fahrenheit. The mean temperature for the month was 45.2 degrees, which is 2.3 degrees above normal for September. On Sept. 3, the high for the month, 67 degrees, was reported. It was the 66 degrees on Sept. 1, the 61 degrees on Sept. 8, and the 62 degrees on Sept. 9 that broke record highs for the respective dates. The low for the month, 24 degrees, was observed on Sept. 7. Precipitation was well below normal at just six-hundredths-of-an-inch, which was much drier than the normal 2.51 inches. No snowfall was reported, though normally only four-tenths-of-an-inch occurs in September. Heating degree-days were less than normal at 585 units. The mean monthly wind speed was 7.7 mph at the airport and a high gust came on Sept. 7. It swept in at 31 mph.

King Salmon had a wetter than normal September, with rainfall totaling 3.3 inches for the month. This rainfall was about half an inch above average. No

snowfall was reported in September, which is normally the case. Nighttime low temperatures stayed above average for the most part of the month. The average low was 41 degrees Fahrenheit, almost two degrees warmer than normal. High temperatures were 54 degrees Fahrenheit, slightly cooler than normal. The mean temperature for the month, 47.9 degrees, was warmer by just a half a degree. The high for the month, 62 degrees, came on Sept. 1, while the low of 23 degrees was reported on Sept. 28. With an average monthly temperature close to normal, heating degree-days were just 15 units below average and totaled 505 for the month. Winds averaged almost 7 mph, and a peak gust of 47 mph occurred at the airport on Sept. 6.

On the last day of September, temperatures peaked in Juneau, with an afternoon high of 62 degrees Fahrenheit at the airport. This temperature broke the previous record daytime high for that date. Overall, the month was just half-a-degree cooler than normal at 49.5 degrees, with highs averaging 54 degrees, which was 2.5 degrees below normal. Lows averaged 45 degrees, which was 1.6 degrees above normal. Only once did the mercury dip down to freezing during the month. It occurred on Sept. 24 when the low temperature of 32 degrees Fahrenheit was reported. Conditions were wetter than normal, with rainfall totaling 10.84 inches for the month, which was 3.3 more inches than normal for September. The highest 24-hour total rainfall was 1.87 inches. It came Sept. 28 – 29. Heating degree-days were just 11 units above average at 457. Winds averaged 6.7 mph at the airport, with a prevailing easterly direction. The peak gust of 44 mph came on Sept. 30.

A striking warm-up came the last two days of September in Ketchikan. The temperature rose to 69 degrees Fahrenheit on Sept 30, which was the high for the month. Overall, however, temperatures averaged 53.1 degrees, 1.2 degrees cooler than normal. Highs and lows averaged 59 degrees and 49 degrees, respectively. The low for the month occurred on Sept. 22, with a reading of 40 degrees Fahrenheit. Precipitation was less than half of the normal September total, with only 5.41 inches reported at the airport. This amount was well below the normal 12.18 inches.

This is preliminary climatological data that was compiled by Dr. Martha Shulski at the Alaska Climate Research Center, Geophysical Institute, University of Alaska Fairbanks. For more information on weather and climatology, contact the center at 474-7885 or visit the center web site at http://akclimate.org. Please report any errors to webmaster@akclimate.org.