With 2007 finally over, we can wipe our collective brow in relief.

VIDEO: Climatologist Randy Cerveny talks about 2007 and what's in store for 2008

GRAPHIC: How the 2007 average temperature compared to previous years

This past year was the second-hottest ever in the Valley’s recorded weather history, which dates back to the 1890s. According to the National Weather Service, 2007’s average temperature was 76.4 degrees — 2.2 degrees above normal and just a shade less than the 77 posted in 1989.

People don’t go by averages, though.

Instead, residents will remember the month of 110-plus-degree temperatures, highs in the 90s during baseball spring training in March and more than a week after Halloween.

Of Phoenix’s top 10 warmest years, six have come in this decade, and weather experts believe nobody should be surprised if 2008 continues that trend.

“I would imagine we will have low temperatures (in the summer) in the lower 90s, we will have high temperatures in the 110-plus range,” Arizona State University climatologist Randy Cerveny said Wednesday. “We do live in a desert, after all.”

Tony Haffer, in charge of the National Weather Service’s Phoenix office, had a more cynical spin: “It’s probably fair to say it’s not going to get much cooler.”

There’s evidence to back that statement: Not since 1998 has Phoenix enjoyed a cooler-than-average year.

What’s causing the rising temperatures isn’t just that we live in a desert, but that we live in a booming desert megalopolis measuring almost 60 miles from Johnson Ranch to Sun City West. Cerveny said all that asphalt, concrete and stucco absorbs heat during the day, creating an effect known as the urban heat island.

“Consequently, the city is a lot hotter, on the order of about 5 to 8 degrees warmer than the outlying deserts,” Cerveny said. “So, we end up with much warmer temperatures than we did a hundred years ago, say, when this was all desert.”

In 1907, Phoenix’s average temperature was 69.6 degrees.

Haffer noted the heat island asserts itself during summer nights. Early-morning temperatures are on the rise, as seen by the 35 record high minimums set last year. For comparison, only 17 days saw previous highs broken.

Other factors raising temperatures include Arizona’s lengthy drought (moist air levels off extreme highs and lows) and global warming, Cerveny said.

The Valley’s rainfall in 2007 fell short of the norm yet again. The official gauge at Phoenix Sky Harbor International Airport took in 5.05 inches, just 60 percent of normal.

This is the ninth straight year, and 11th in 12, when the precipitation fell short of average.

But Cerveny, looking at when the rain fell, noticed something odd.

Currently, a La Niña pattern is cooling the waters of the tropical Pacific Ocean. Going by history, Arizona’s winter should be warm and dry, and forecasts as early as last summer predicted as much.

Except Arizona’s winter, so far, is cool and wet. During a nine-day span beginning Nov. 30, Phoenix received more than 2.3 inches of rain — more than half the year’s total. And another storm is expected this weekend.

Also, December’s average temperature was below normal.

“We’re seeing storms, we’re seeing cold air coming down here into the state, when there isn’t any reason for them to do that,” Cerveny said.

“Frankly, it tells us we still have a lot to learn about what makes our climate system work — particularly in the Southwest.”

The Valley’s short-term forecast is calling for the possibility of rain this weekend, followed by lower temperatures.

A series of weak impulses sliding across the desert today and Friday will drag moisture in from the Pacific. Then, an intense low-pressure system will sweep down from the Northwest, spreading precipitation from northern Arizona in a southeasterly direction.

The rain that falls in the Valley will come Saturday night into Sunday morning, and late Sunday into early Monday.

The system could bring as much as half an inch of rain to the Valley, but the state’s higher elevations could see plentiful snow.

Once the system clears out by Monday, daytime highs will fall into the low 60s and overnight lows will struggle to top 40 degrees.