The potential for locally dangerous and disruptive thunderstorms will exist over the Midwest into Wednesday evening.
Areas from Central America to southeastern Mexico, western Cuba and southern Florida will be on alert into next week as a tropical system may form.
Warmth will build and evolve into a heat wave across a significant part of the western United States this week.
Rounds of heavy thunderstorms will raise the risk of flooding across the south-central United States into Friday.
Temperatures and humidity levels will throttle back as dry air expands southward in the northeastern United States through the middle of the week.
The next round of primary elections will take place on June 7 with six states heading to the polls.
Philadelphia, PA (1998)
A tornado in northeast Philadelphia; one building collapsed and houses were unroofed, windows blown out of parked cars.
New Haven, CT (1812)
Latest blossoming of apple trees during this period (1794/1985).
Eastern Great Lakes (1843)
Snow fell and whitened the ground at Cleveland, OH, and Buffalo and Rochester, NY.