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:
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Tuesday 30 June – France v Sweden, New Jersey – 30C (86F)
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Thursday 2 July (overnight Thursday into Friday for UK viewers) – Portugal v Croatia, Toronto – 31C (88F)
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Friday 3 July – Argentina v Cape Verde, Miami – 31C (88F)
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Friday 3 July (early Saturday for UK viewers) – Colombia v Ghana, Kansas City – 32C (90F)
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.
Analysis by Dale Johnson, Football issues correspondent
Fifa has outlined measures that will be deployed during heatwave conditions but there is no suggestion any of the games could be halted or rescheduled.
It has already introduced climate-controlled benches for technical staff and substitutes at all outdoor matches, including the provision of water and electrolyte drinks, ice, cold towels, fans, mist and shade.
With the threat of a heatwave evident, Fifa outlined strategies and management of heat-related illnesses to the chief medical officers of every country during a workshop held in March.
It says the tournament schedule was created following “extensive heat-risk analysis carried out by FIFA at each location”.
This resulted in limiting outdoor matches during the hottest parts of the day, with matches expected in warmer windows prioritised for covered stadiums where possible.
But that policy cannot mitigate against the truly extreme temperatures – for players and for supporters.
