Northeast hit with potentially record-breaking heat this weekend

The Northeast is getting hit with a potentially record-breaking heat wave this weekend.

Heat advisories are in effect for cities including New York, Philadelphia, Boston and Hartford, Connecticut, as heat index values -- what the temperature feels -- may top 100 degrees.

Temperatures are expected to soar into the mid- and upper-90s across much of the Northeast on Saturday and into Sunday -- about 20 degrees higher than is typical for this time of year for some of the region.

Boston Mayor Michelle Wu declared a heat emergency for Saturday and Sunday due to the unseasonably high temperatures and humid weather forecasted.

With temperatures expected to be in the low- to mid-90s, the city has opened cooling centers and splash pads at parks and playgrounds ahead of schedule.

"We're working quickly to make sure all of our Boston residents and families are protected during this weekend's extremely hot weather," Wu said in a statement. "As we head into summer, it is clear that earlier, more frequent extreme heat days from a changing climate are a risk to our health and communities."

In New York City, over 600 spray showers have been activated across the city in anticipation of the high temperatures, with a heat advisory issued through 8 p.m. Saturday.

This year's Preakness Stakes will be the hottest in recent memory, with forecasted high temperatures in the mid-90s and heat indices approaching 100 in Baltimore on Saturday. The temperature is usually in the mid-70s this time of year.

"The abrupt beginning of hot temperatures early in the season after a relatively cool spring brings an increased risk of heat illnesses unless proper precautions are taken for those working or recreating outdoors," the National Weather Service said in a statement for the Baltimore and Washington, D.C., region. "Since many outdoor events are planned this weekend in the region, be aware of the heat, and take extra precautions if you work or spend time outside this weekend."

Racetrack officials will track the temperature, humidity and wind speed to determine whether to delay or cancel the horserace, according to the Baltimore Sun.

The Northeast will see some relief after a cold front comes through on Sunday, bringing temperatures back to more seasonable levels by Monday.

ABC News' Daniel Amarante contributed to this report.