A number of spectators also succumbed to the searing heat as they waited to pass through security for sporting events.
But the heatwave that has baked Scotland for most of this week was giving way to cooler, cloudier conditions this weekend.
On the eve of the busiest weekend of the Games for the city's transport infrastructure, the scorching conditions wreaked havoc on rail services between Glasgow and Lanarkshire, in particular - though other routes also faced disruption yesterday.
Passengers trying to travel eastbound on the Motherwell/Hamilton and Bellshill lines were among the worst affected as temperatures of up to 27C caused points failures and subsequent signalling problems during the afternoon. Trains were diverted to skip Bellshill station.
Network Rail said a temperature of 43C (109F) was recorded on one section of the track near Glasgow.
Points are the mechanical installations along a track which shift to guide a train from one track to another. Hot weather causes points failure by making the metal of the track expand and then contract as temperatures cool.
A spokesman for Network Rail said: "There have been signalling problems in and around Glasgow caused by points failures along the line, especially on Lanarkshire routes.
"Many of the points failures are heat-related. One point on the line reached 43C (109F) today - with intense sun creating high temperatures on the track - and this can cause points to fail because of expansion and contraction.
"There have been speed restrictions in place because of points failures so trains are running more slowly than normal."
Although most of the Lanarkshire faults were resolved by rush hour, commuters faced knock-on delays to services of up to an hour.
There was also disruption to services between Glasgow and Lanark due to a level-crossing problem, while services between Edinburgh and Glasgow Queen Street were also affected.
Trains between Falkirk Grahamston and Glasgow Queen Street were running from Camelon due to a points failure.
Meanwhile, First Aid staff at the Emirates Arena said yesterday they had been "really busy" dealing with heat-induced ailments as temperatures soared to 27C (80 degrees).
At least 20 people were treated by medics after fainting in the heat, many while waiting to pass through security.
Volunteers were handing out bottles of water and directing others to free water fountains.
With increased numbers attending cycling events at the Velodrome, spectators were facing longer waits to pass through the barriers.
However, the increase in waiting times did not dampen enthusiasm for proceedings.
Norman and Margaret Smith, from Victoria, Australia, who are in Glasgow for Games, were at the Emirates to support their son Ross Smith, who was competing in the badminton events. Norman said: "We arrived just as the queue started moving but I think, before that, it was taking a bit of time to go through. It's been great though, no complaints. Everyone is very welcoming."
Outside Tollcross International Swimming Centre, Suzanne and Rod Fullalove were waiting anxiously to watch their daughter Jessica Fullalove, who was competing for a place in the 100m backstroke as part of Team England.
At 17, Jessica, from Manchester, is the youngest swimmer in the squad.
Suzanne said: "Your heart is in your mouth when you watch them compete."
Meanwhile, there was more praise for the organisers from ticket-holders outside the centre.
Ann Marie Fraser, from Aberdeen, who has two young children, Jessica, six, and Ben, eight, said: "We were at Glasgow Green yesterday and the range of events they put on was incredible. It's like a mini festival. Everyone is so welcoming."