Brrrr! Cold front has many asking ‘What happened to the heat wave?’

Missing that heat wave?

Barely out of a summer sizzle, many Americans are now reaching for their sweaters as an advancing cold front causes temperatures to plunge 5 to 20 degrees below July averages.

"The quick change of air mass to cool Canadian air is unusual in that the northwest flow is also going to last a week or two," said Bill Karins, a meteoroligst for NBC News. "Typically a cool spell in the summer would last one or two days."

The cold is expected to bring storms through the Midwest on Thursday, then leave behind a chill. In Chicago, where the heat index was over 100 degrees one week ago, Saturday's high temperature is predicted to be only 69 degrees.

On Friday, highs in North Dakota and north Minnesota will struggle reach the mid-60s, the Weather Channel reports. And in Milwaukee, where three people reportedly died of heat-related causes last week, forecasters predict weekend high temperatures will hover in the low 70s. 

“It’s a welcome reprieve from the heat that we had across the country in the last couple of weeks,” said Jim Keeney, a meteorologist for the National Weather Service. 

A cold front following a heat wave is not necessarily rare in the Midwest, according to Keeney, but the duration and the push southward is out of the ordinary.

The front will likely hit as far as south as Oklahoma and Arkansas over the weekend, causing temperatures to drop 5 to 10 degrees colder than usual. The region, which has suffered significant drought in the past few years, welcomes the much-needed rain the front will bring.

But the cold isn't good news for everyone. In Boston, where the heat index was 105 last Friday, Thursday’s forecast says temperatures won’t break 70. The weekend also carries with it the threat of storm to beach-goers from Cape Cod all the way to the Virginia coast.

As for Thursday's cold spot: Saranac Lake, N.Y., in the heart of the Adirondack Mountains, sank to a crisp 33 degrees before dawn.