Extreme heat is set to hit lower parts of the Grand Canyon from Monday, the US National Weather Service (NWS) warned, with temperatures projected to exceed 100F (37.7C).

An alert published on Saturday will be in effect from 10am local time on Monday through 7pm on Tuesday.

Temperatures could climb as high as 112F (44.4C), according to the NWS’s office in Flagstaff, Arizona, compounding concern about warm conditions. Three hikers in the national park have recently died in heat-related incidents.

Forecasters warned “dangerously hot conditions” were possible below 4,000ft, with daytime temperatures expected to range between 97F (36.1C) at Havasupai Gardens to 111F (43.8C) at Phantom Ranch.

“Most individuals will be at risk for heat-related illnesses without effective cooling or adequate hydration, especially with prolonged outdoor exposure,” the agency’s Flagstaff office said. Such “extreme heat watch” notices are “reserved for only the hottest days of the year”, it added, and “issued when temperatures could rise to dangerous levels”.

Weather officials urged hikers to avoid being in the canyon between 10am to 4pm, and advised against physical activity.

The warning follows a series of recent heat-related deaths in the park. On Friday, the National Park Service (NPS) said that Grand Canyon park rangers and emergency personnel responded to two separate heat-related incidents, on 12 June and 16 June, that resulted in three deaths.

“In both cases, the deceased hikers were hiking trails in the Inner Canyon, where temperatures can exceed 109F in the shade during midday hours,” the agency said.

According to park officials, on 12 June, a 72-year-old male “succumbed to symptoms of heat-related illness” along the South Kaibab Trail. And on 16 June, in a separate incident, a 67-year old man and a 68-year-old woman also appeared to have “succumbed to symptoms of heat-related illness” on the North Kaibab Trail, although the investigation is “still ongoing”.

“Despite rapid response and aerial support, all three individuals were found deceased when responders arrived,” the statement said.

Earlier this month, an 18-year-old man also died in the park after experiencing what the authorities described as “heat-related symptoms”.

“Hiking in Grand Canyon can be a challenge for anyone, especially during the heat of summer,” the park service said on Friday. “Recent increase in heat-related incidents comes as summer temperatures in the Inner Canyon have reached dangerous levels, creating conditions that can quickly overwhelm hikers during the hottest parts of the day.”

Elsewhere in Arizona, evacuation orders have been issued for some communities between Sedona and Forest Highlands as firefighters work to contain a the Pocket fire located just north of Sedona in the Oak Creek Canyon area.

Meanwhile, extreme heat watches have also been issued for parts of Oregon from Monday through Tuesday evening, and for portions of California from Tuesday evening through Thursday, with forecasters warning of potentially dangerous temperatures.

In Texas, the NWS office in San Angelo, said that “triple-digit heat” can be expected from Sunday into early next week.

Heat advisories are currently in effect for parts of Alaska, Puerto Rico, Florida and Texas. The advisories have also been issued for Sunday in portions of Arkansas, Oklahoma, Texas and New Mexico.

The heat comes as the US is currently co-hosting the Fifa World Cup, alongside Mexico and Canada. Earlier this week, a Guardian analysis found two matches of the tournament’s first round were played at a level of severe heat that a football players’ union has previously said should trigger the delay or postponement of games.