Northeast temps continue to cook. Is it a heat dome or heat wave?

Temperatures are rising near or over 100 in cities across the Northeast and Midwest.

Millions across the U.S. are suffering the effects of this week's heat wave, including New Jersey and Pennsylvania, with temps climbing into the high 90s.

Cities across New Jersey are dealing with temps pushing over 93 degrees while Pittsburgh is expected to hit a record-breaking temp of 98 degrees today, per Accuweather forecasts.

The forecasts are calling for those temps to creep even higher as the week unfolds. Philadelphia is expected to break 100 degrees by Friday.

Here's what you should know about the heat and what's coming.

What is a heat dome? How is it different from a heat wave?

A heat dome is a weather phenomenon of extreme heat that becomes trapped when strong high pressure atmospheric conditions remain still for a longer than usual amount of time.

NOAA explained, "Under high pressure, the air subsides — sinks — toward the surface. This sinking air acts as a dome capping the atmosphere."

"This cap helps to trap heat instead of allowing it to lift. Without lift, there is little or no convection and, therefore, little or no convective clouds — cumulus clouds — with minimal chances for rain. The end result is a continual build-up of heat at the surface that we experience as a heat wave."

A heat wave is a period of abnormally hot weather that lasts two or more days, and is usually measured relative to the historical averages in the area for that season. It can also be described as extreme heat.

A heat advisory is usually issued with 12 hours of the onset of extremely dangerous heat conditions versus.

An excessive heat watch advises you to prepare for an excessive heat event within the next 24 to 72 hours versus an excessive heat warning, which means take action now to guard against the heat.

This article originally appeared on Pocono Record: Record high temps possible across the US: Heat wave, heat dome ahead