Fall 2009 has been one screwy season.

First came September, the second-hottest in more than 75 years of recordkeeping. It was followed by October, the second-coldest on record. And now we're heading into November with weekend temperatures forecast for the mid 60s instead of the 40s and 30s we should be seeing this time of year.

"Maybe because we put up with cold in October, the rest of the winter will treat us more kindly," said Keith Meier, meteorologist in charge at the National Weather Service office in Billings.

It's not entirely idle speculation.

El Niño appears to be strengthening, he said, and the normal signature for the phenomenon in Eastern Montana is a warm winter. El Niño is an unusual warming of the tropical Pacific Ocean, affecting climate worldwide.

October weather was more than a little strange. It wasn't just a little cooler than normal; the mean temperature of 41.3 degrees was 6.8 degrees colder than normal. Only October 1969 had a lower mean temperature, at 40 degrees.

Daytime highs were especially cool, averaging 49.9 degrees, fully 9 degrees below normal. Minimum daily temperatures averaged 32.6, which is 4.6 degrees below normal.

"Two things stand out," Meier said. "The pattern in the last two years has been a big October snow event. The second thing is the record cold on the 9th through 12th. It was unprecedented both in magnitude and duration."

Record low temperatures struck on each of those days, starting with a low of 18 degrees on the 9th and falling to 13 degrees on the 12th. Highs on those days were 35, 24, 23 and 29 degrees, consecutively.

"How unusual is it to have low temperatures below 20 degrees in October?" he asked. "I checked. The average is one day. This year we had four. Normally it would be at the end of the month. This was early cold by about two weeks."

Three days during October had highs in the 20s. Meier said the average number of such chilly daytime temperatures is zero. Three days had high temperatures in the 30s, seven in the 40s, thirteen in the 50s, three in the 60s and two in the 70s. Normal October highs start in the mid 60s and cool down to the low 50s by the end of the month.

"Normally, October produces 17 days with temperatures of 60 or above," Meier said. "This year there were only five."

The warmest days of 74 degrees were reported Oct. 17 and 18. The coldest temperature was 13 degrees on Oct. 12.

Before the frigid air arrived, Montana was buried in its first snowfall of the season. Most of September's precipitation fell during a four-day period starting on Oct. 4 with 0.2 inches. The next day, 0.73 inches of moisture was measured. On Oct. 7, 0.25 inches was recorded.

Snowfall for the month was 6.6 inches, or 2.4 inches above average. Most of it, 4.6 inches, fell on Oct. 5.

Contact Lorna Thackeray at lthackeray@billingsgazette.com or 657-1314.