(NewsNation) — More than half of the country is likely to see rain Sunday. Thunderstorms will accompany warmth and humidity across the Northeast states. Areas of heavier thunderstorms are expected across the mid-Atlantic, Ohio Valley and Upper Midwest.

Storms along the Appalachians can renew flooding concerns for areas that have been hit hard over the last few weeks, especially in eastern Kentucky. A dense fog advisory has been issued to the east of these storms, mostly in western Virginia, southeast West Virginia and northwest North Carolina.

Severe storms in the Upper Midwest can also cause areas of flooding. Flash flood warnings and flood watches have been issued for areas in Wisconsin, northern Illinois, northeast Iowa and the southeast corner of Minnesota.

Spotty afternoon thunderstorms are expected across much of the Southeast and Gulf Coast. A flood watch is also in effect for central-eastern Colorado.

Dangerous heat is expected across parts of the Pacific Northwest, middle Mississippi Valley, Central Plains and Northeast coast, according to the National Weather Service. Heat advisories are in effect for parts of the Central Plains, Northeast and Pacific Northwest. An excessive heat warning has been issued for the state of Washington.

High temperatures across the southern Plains are expected to be in the mid- to upper 90s, but can surge into the triple digits in spots. Temperatures across the Western deserts can also reach into the upper 90s and 100 in places, mostly south.

Monsoonal moisture across the Four Corners region can lead to areas of afternoon thunderstorms.

Meteorologists are watching a tropical wave in the far eastern Atlantic, but there are currently no organized systems in the Atlantic basin. Tropical waves currently located along 80 west, 63 west, 27 west and near 40 west have some disorganized shower and thunderstorm activity associated with them.

However, none of these waves are expected to develop further. Satellite imagery also shows a tropical wave emerging off the western coast of Africa. As this wave tracks westward over the next few days, there are signs that it may develop and organize further into a tropical depression or storm as it moves into the central Atlantic later this week.

The Associated Press contributed to this report.