Tomorrow's the day.

After a high of 97 degrees at the Portland International Airport on Tuesday, Portland area temperatures are expected to make the jump across the century mark and beyond Wednesday.

Portland-area heat records could fall as temperatures continue to rise Wednesday, meteorologists say.

The all-time record high recorded in Portland is 107 degrees. Three days hit the record -- Aug. 8 and 10 in 1981 and July 30, 1965. The daily record for Aug. 2 is 96 degrees, recorded in 1986. For Aug. 3, it's 99 degrees, recorded in 1952.

This week, the National Weather Service's seven-day forecasts predicts a likely high near 105 on Wednesday and Thursday then 100 on Friday.

And that's not even as hot as initially expected. Over the weekend, weather service models predicted a slim chance of 113 degree heat. But now, as the heart of the heat wave nears and forecasts tighten up, that's no longer within the range of expected temperatures, said meteorologist Evan Bentley.

Now, Bentley said, the range of anticipated highs is lower: between 103 and 109 degrees.

"As we are getting closer to the event, models are zeroing in to about 105 degrees, plus or minus a couple degrees," he said.

Only nine days have reached 105 or higher since the weather service started keeping records at Portland International Airport in 1940.

Forecasts models are similar to a bell curve, Bentley said. The majority of the models predict temperatures between 104 and 107 degrees, but a few outliers predict slightly hotter or cooler.

So, Portlanders most likely won't see the mercury reach 109. There's less than a 10 percent chance temperatures will reach the high end of the predictions, Bentley said.

That's good news for people who are dreading the heat. But if you're hoping for the off-chance the predictions will be wrong, bad news: It's about certain the high won't dip below 100.

"We're past the point where the forecast could change that dramatically," Bentley said. "Confidence is high that temperatures will be over 100."

Regardless of whether Portland hits the 107 record, a few degrees likely won't make a perceptible difference for most people, Bentley said.

"Whether it's 103 or 108, it's going to be hot," he said.

People should prepare for the heat accordingly, Bentley said.

Elderly people and those without air conditioning are most vulnerable to heat-related illnesses. The weather service advises people to drink plenty of fluids, stay in air-conditioned rooms and out of the sun and check on relatives and neighbors who don't have AC.

Cooling centers are available across the metro area for people who don't have air-conditioning.

-- Samantha Matsumoto

503-294-4001; @SMatsumoto55