ASHEVILLE, N.C. (828newsNOW) — Happy first day of summer! Its arrival Friday came with hot and increasingly humid weather across the Carolinas, according to the National Weather Service.

Forecasters said conditions will remain hot but less humid through Saturday, with a return of muggy air and higher temperatures starting Sunday as a strong upper-level ridge builds over the region. Afternoon and evening thunderstorms are expected to increase by midweek.

The heat and humidity will gradually intensify into early next week and linger into the following weekend, the agency said in its forecast.

The Weather Service urged residents to be aware of heat-related alerts that may be issued in the coming days:

Extreme Heat Warning: Issued when extremely dangerous heat conditions are expected or occurring. Avoid outdoor activities, especially during the heat of the day. If you must be outside, be sure to drink plenty of water and take frequent breaks in the shade. Stay indoors in an air-conditioned space as much as possible, including overnight. Check on family and neighbors. Issued when the heat index is expected to reach or exceed 105°F for an extended period (often 48 hours or more) or when afternoon heat index values are between 105°F and 110°F for an extended period. These warnings are for extremely dangerous heat conditions where heat stroke is highly likely.

Extreme Heat Watch: Indicates the potential for a dangerous heat event. Residents should begin preparing by planning to limit outdoor exposure and identifying nearby cooling shelters if needed.

Heat Advisory: Signals heat conditions that are hazardous but below warning thresholds. People should stay hydrated, limit time outside and rest in the shade or cool indoor spaces. Issued when the heat index (how hot it feels, taking into account temperature and humidity) is expected to reach 105°F or higher or when temperatures reach 100°F or higher, especially in areas west of the Blue Ridge mountains. These advisories typically cover a 24-36 hour period. They are issued to alert the public to the potential dangers of heat-related illnesses like heat cramps, heat exhaustion, and heat stroke.

Heat Index: A measure of how hot it feels when relative humidity is combined with the air temperature, according to the National Weather Service. It’s important to pay attention to heat index values because they can significantly increase the risk of heat-related illnesses.

Vulnerable Populations: The National Weather Service advises that young children, older adults, people with chronic illnesses, and those who are obese are particularly vulnerable to heat-related illnesses.

The forecast, according to the National Weather Service:

  • Tonight: Partly cloudy, with a low around 63. West-southwest wind around 5 mph becoming calm in the evening.
  • Saturday: Sunny, with a high near 88. Calm wind becoming south-southeast around 5 mph in the afternoon.
  • Saturday night: Mostly clear, with a low around 66. Light south-southeast wind.
  • Sunday: Sunny, with a high near 91. Light and variable wind.
  • Sunday night: Mostly clear, with a low around 68.
  • Monday: Sunny, with a high near 93.
  • Monday night: Mostly clear, with a low around 68.
  • Tuesday: Sunny, with a high near 94.
  • Tuesday night: Partly cloudy, with a low around 68.
  • Wednesday: Sunny, with a high near 94.
  • Wednesday night: A 30 percent chance of showers and thunderstorms. Partly cloudy, with a low around 68.
  • Thursday: A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 93.