The first major heat wave of the summer is building just in time for the weekend. From the Rockies to the Northeast, temperatures will climb well above 90 degrees. In the central part of the country, where the heat is most oppressive Thursday and Friday, highs will reach the triple digits.

And, after a brief reprieve, there are signs that this heat wave may stick around for more than a week.

High pressure will build across the Lower 48 on Thursday and Friday. Temperatures will run 10 to 20 degrees above normal for this time of year in the Plains states on Thursday. The most intense heat will focus in on the Central Plains from Nebraska south into Texas. Across that entire region, high temperatures will exceed 100 degrees.

On Friday, extreme heat will spread east into the Great Lakes. In northern Wisconsin and Michigan’s Upper Peninsula, temperatures will be more than 20 degrees hotter than normal. Highs will reach at least the 90s across much of the Midwest.

The ridge of high pressure will be at its strongest Saturday and Sunday as it shifts focus to the East. Temperatures will climb well into the 90s, and the heat index will reach triple digits. Sunday will be the hottest day for New York City, where the afternoon temperature will soar to 97, and the heat index will top out at 105.

In Washington, highs could reach at least 90 for nine days in a row, potentially longer, beginning Friday. The capital’s longest streak of 90-degree days is 21, which occurred in 1980 and 1988.

Saturday highs (and heat index)

Washington — 95 degrees (99)

New York City — 92 degrees (94)

Boston — 91 degrees (93)

Sunday highs (and heat index)

Washington — 96 degrees (102)

New York City — 97 degrees (105)

Boston — 89 degrees (95)

Record highs are likely to be broken over the next several days. This list, compiled by weather.com, includes some of the more notable records on the chopping block:

  • Thursday: Denver (99 degrees); Cheyenne, Wyo. (94 degrees)
  • Saturday: Detroit (96 degrees); Rochester, N.Y. (96); Burlington, Vt. (93)
  • Sunday: Concord, N.H. (99); Syracuse, N.Y. (94); Burlington (96); Worcester, Mass. (94); Buffalo, N.Y. (93); Caribou, Maine (89)

This heat wave will be brutal because of the temperature, but it’s packing an extra punch with extreme humidity.

The dew point — a measure of how much moisture is in the air — will be in the low 70s across most of the area affected by the heat wave, making it even more oppressive and potentially dangerous. Combined with hot temperatures, high dew point leads to extreme heat index. Sometimes referred to as the “feels-like” temperature, heat index takes into account the humidity and is more representative of how hot the air feels than the temperature alone.

Given the forecast for highs in the 90s and 100s alongside dew points in the 70s, the National Weather Service issued widespread heat advisories and excessive heat warnings Thursday, covering 15 states in the central United States.

A weak low-pressure system and associated cold front could provide modest relief early next week, but forecast models anticipate high pressure to return quickly. Both the European and the American (GFS) models predict extreme high pressure to continue across the eastern half of the country through next weekend.