With ‘feels like’ temperatures up to 45C (113F) in parts of the United States this week, some World Cup matches could have heat indexes exceeding the threshold where global players’ union Fifpro consider it too unsafe for play.

Dangerous heat is building across the US and Canada, according to the National Weather Service (NWS).

With air temperatures widely in the high 30s Celsius and close to 40C (104F), accompanied by high humidity, it will make the weather very uncomfortable with possible health-related impacts.

Temperature records could even be broken in some eastern States at the end of the week.

A large heatwave will intensify as the week progresses, covering much of central and eastern US states and through much of Canada.

Temperatures in excess of 32C (90F) are widely expected.

Add in the humidity and it will actually feel like temperatures are up to 46C (115F) across portions of the Southern Great Plains, mid-Mississippi valley and eventually into parts of the mid-Atlantic, according to the NWS.

Overnight temperatures may not fall below 20C (70F) – classed as a “tropical night” by meteorologists.

The extreme heat will also affect eastern Canada with temperatures forecast to be up to 10C (18F) above average in Ontario and Quebec.

Not all of the round of 32 matches in the World Cup will be affected by the heatwave but there will be some notable games to keep an eye on.

The hottest weather will be in Texas which will mostly impact fans travelling to and from the air-conditioned stadiums in Houston and Arlington.

This will also be the case for England v DR Congo on Wednesday in Atlanta where it will also feel hot and humid outside of the air-conditioned stadium.

It will obviously feel much more pleasant inside the stadiums for players and fans.

Some of the matches where the heat could be an issue are:

The games on Friday in Miami and Kansas City could be especially uncomfortable as the high humidity here mean it feels hotter than the actual temperature, feeling up to 40C (104F).

In the official measure of how heat and humidity affects the human body – known as Wet Bulb Global Temperature (WBGT) – both these matches may have an index close to the threshold that Fifpro considers it too unsafe to play.

By this weekend, the heat will peak across eastern areas of the US and Canada, pushing temperatures way above average and close to records.

In New Jersey and Philadelphia the air temperature will be close to 40C (104F). But it will feel more like 45C (113F).

There are two ‘last 16 games’ here over the weekend and while the extreme heat will have eased slightly, the “feels like” temperature will still be above 40C (104F).

The WBGT for these matches could be above the Fifpro threshold for safe play.

With high temperatures and high humidity you would expect there to be thunderstorms.

Initially, most of the wet weather and storms will be over the Northern Plains and Upper Midwest – away from the World Cup host cities.

Later in the week, though, there may be thunderstorms developing in the heatwave area, which could affect some of the matches.

Thunderstorms only have to be within an eight mile (13km) radius of a stadium for a match to be suspended so that players and spectators can seek shelter.

For England’s game against DR Congo in Atlanta on Wednesday there is currently a small risk of a thunderstorm which may affect the match. The risk is higher later in the afternoon once the game has finished.

There is a also a high chance of a thunderstorm affecting the Argentina v Cape Verde last 32 game in Miami on Friday.

As the extreme heat and humidity in New Jersey and Philadelphia peaks, thunderstorms are also in the forecast here over the weekend.