PORTLAND, Ore. -- Just a week after the start of summer, Oregon was hit with its first heat wave of the season.

"It may not seem like it, but it was another hot day today," KGW Meteorologist Joe Michaels said Sunday. "The valleys reached up to near 90, and portions of Central and Eastern Oregon were much hotter – The Dalles hit 106."

With moisture rolling in, storms started to pop up Sunday afternoon. The storm threat will persist overnight, Michaels said.

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"Tomorrow will bring hot sunshine to the Metro area, with highs still in the upper 80s. The storm threat tomorrow will shift to the east, and be isolated to the Cascades and Central and Eastern Oregon," he said.

By Tuesday, temperatures are expected to cool down as more marine air rolls in. Highs are expected in the lower 80s Tuesday and Wednesday, and by week’s end, highs will likely be in the upper 70s.

"Some showers are likely, too, for Thursday and into the holiday weekend. There could even be some isolated thunderstorms," Michaels added.

The heat hit statewide this weekend, with Salem, Hillsboro, Medford and The Dalles all topping triple digits.

The temperature reached 100 at Portland International Airport on Saturday. eclipsing a record set five years ago.

A heat advisory remained in effect on Sunday.

Except for a short hot spell in mid May, it has been an unusually cold spring.