September third-wettest month in 137 years

Enough rain fell throughout the Chicago area in September to make it the third-wettest month in 137 years.

But it still wasn't the wettest September.

Despite a soggy Monday that nearly dumped another inch of rain on the region, the moisture level fell a half inch short of the September record of 14.17 inches of rain in 1961. The official regional total for September 2008 from the rain gauge at O'Hare Airport was 13.63 inches, said National Weather Service meteorologist Charles Mott.

The weather service mans the O'Hare station around the clock, but also utilizes dozens of rain gauges around the region to help track the effects of various storm systems that travel through the area. That's why some rain gauges in the region may have higher or lower rainfall totals than O'Hare, Mott said. The O'Hare equipment also is more sophisticated than the other unmanned weather stations, he said.

The all-time rainfall record occurred in August 1987 when 17.1 inches of rain doused the region, including about 10 inches that fell in a three-day span, Mott said.

Last month, it rained just 11 days, but an 8.45-inch deluge between Sept. 12 and Sept. 15, which caused extensive flooding throughout the area, set the pace.

"It's just when it rained, it really rained," Mott said.

An average September sees only about 3.27 inches of rain. The excess moisture in the region shouldn't impact fall colors, tree experts said.

"The cool weather we've been having is going to play a larger role than the rain," said Doris Taylor, a plant information specialist at Lisle's Morton Arboretum. "We're going to be seeing leaves changing colors sooner this fall because of the colder temperatures we're getting."

Mott said the October forecast looks normal, and he doesn't anticipate the region getting more than the 2.71 inches of rain the month averages.

Wet enough for you?

Five days that helped make September the third-wettest month in 137 years.

Sept. 15: 6.64 inches

Sept. 4: 2.9 inches

Sept. 14: 1.44 inches

Sept. 8: 1.23 inches

Sept. 29: .82 inches

Source: National Weather Service