The humidex value rose to a record-breaking 38.7 C at the St. John's airport on Wednesday.
The previous record humidex was 38.5 C on July 6, 1983.
However, today's temperature of 29.5 C failed to break the record high of 31.5.
CBC Meteorologist Ryan Snoddon says Thursday will likely be a record-breaking day, with the temperature forecast to be close to 30 C, and a humidex near 40.
"Tomorrow's July 31 record of 29.3 C, set back in 2004, will also likely be broken."
Snoddon said the 30-degree mark at the St. John's weather station is tough to come by — it has reached that mark just nine times over the past 72 years.
"A couple of other records I'm keeping an eye on are the all-time temperature record of 31.5 C and the all-time humidex record of 38.5 at St. John's YYT," Snoddon said.
"Both records were set on the same date, back on July 6, 1983, and are certainly at risk of being broken over the next two days."
Protest at senior's home in Bonavista
The heat sparked a protest by staff at a long-term care home, Golden Heights Manor, in Bonavista.
The workers are worried about their safety and well-being along with that of the 70 seniors at the home.
Most of the building doesn't have air conditioning.
About two dozen workers said they had reached a breaking point and decided to protest during their lunch hour to draw attention to the conditions inside. Most of the staff held placards criticizing Eastern Health.
The health authority said it recognizes the extra burden the heat and humidity can put on its staff and is monitoring the conditions "to ensure the safety of staff and residents."
Eastern Health said it's taking measures to minimize discomfort by putting fans throughout the building, offering ice and water to residents and giving extra breaks to staff. It also says there is one air conditioned cooling room for staff and residents. A second cooling room is being created.
Warm, humid air mass over most of Newfoundland
Meteorologist Allison Sheppard, who works with the Gander weather office, said a warm, humid air mass will remain over much of the island for the next 48 hours.
"There are several areas that have values into the high 30s, but it looks like through Gander, in through St. John's, they're going to be in the very high [range], approaching 40 for humidex values."
The heat and humidity will affect the following areas:
- Avalon Peninsula North
- Bay of Exploits
- Bonavista North
- Bonavista Peninsula
- Buchans and the interior
- Clarenville and vicinity
- Deer Lake - Humber Valley
- Gander and vicinity
- Grand Falls-Windsor and vicinity
- Green Bay - White Bay
- St. John's and vicinity
- Terra Nova
Environment Canada reminds anyone taking part in strenuous outdoor activities over the next two days to drink plenty of fluids to remain hydrated, and suggests rescheduling outdoor activities to cooler parts of the day.