What difference does the heat make in Brazilian league matches?

Everyone keeps banging on about the heat in Brazil but isn’t it always hot? Spain 1982 would have been roasting in June. I remember running home from school to catch the game at 4:15pm and that would have been 5:15pm in Spain and damn hot. Visit Madrid in July and you’ll get an idea of how hot it will be there. Down South it would have been the same as well and the Guardian has an article about one of the semi finals and they say

“Their semi-final was at the Estadio Ramón Sánchez Pizjuán, on 8 July 1982. Kick-off was 9pm but it was a muggy night in Seville, with the temperature in the high nineties.”

 

So in Brazil they say the worst places temperature wise are in the North and that includes 5 venues. I looked to see if any teams from those cities played in The Brazilian Championship in 2013.
Manaus – No team
Fortaleza – No team
Natal – No team
Recife – Nautico
Salvador – Bahia and EC Vitoria

So there are 3 teams and a quick test is to look at the total goals scored when any of these teams played at home and see if they are grouped at one end of the table.

Home TeamFATotal GoalsAv. Goals
AA Ponte Preta1926452.37
Atletico MG3916552.89
Atletico Paranaense3419532.79
Bahia1918371.95
Botafogo3014442.32
Corinthians175221.16
Coritiba FBC2919482.53
CR Vasco da Gama2623492.58
Criciuma2625512.68
Cruzeiro4716633.32
EC Vitoria3220522.74
Flamengo2519442.44
Fluminense FC2824522.74
Goias2716432.26
Gremio2412361.89
Internacional3024542.84
Nautico1435492.58
Portuguesa de Desportos3217492.58
Santos FC2813412.16
Sao Paulo2221432.26
League Total5483829302.45

Bahia and Vitoria are from the same city but at opposite ends of the table and Nautico are only a tiny bit above the league average so it doesn’t look like there is anything there

What about corners?

Home TeamFATotal CornersAv. Corners
AA Ponte Preta94891839.63
Atletico MG1197319210.11
Atletico Paranaense10310020310.68
Bahia89891789.37
Botafogo1299122011.58
Corinthians104811859.74
Coritiba FBC11210021211.16
CR Vasco da Gama1218320410.74
Criciuma10311521811.47
Cruzeiro1377521211.16
EC Vitoria13310423712.47
Flamengo1208620611.44
Fluminense FC1309022011.58
Goias112771899.95
Gremio1179821511.32
Internacional1437922211.68
Nautico999919810.42
Portuguesa de Desportos1259121611.37
Santos FC10910321211.16
Sao Paulo1337420710.89
League Total23321797412910.89

Bahia the lowest and Vitoria the highest and they are from the same city (Salvador).

The sample size here is small and there are many other factors that control how many goals or corners there will be, such as how both teams set out tactically and if they are pressing to score goals or just sit back and look to defend.

My real point here is we have no idea what impact the heat will have. Obviously people won’t be able to run quite so much but does that mean less goals, more goals, the same goals? Does the heat mean people are more likely to make mistakes? Will substitutes coming on around the 70 minute mark be that much fresher? I have no idea about the answers to any of these questions and have not found anyone else who does.