Mercedes driver Lewis Hamilton says daytime practice at the Bahrain Grand Prix is now "a waste of a session", as the heat makes Formula 1 cars "horrible to drive".
Bahrain became a night race from 2014 onwards, having first joined the F1 calendar in '04.
Its sessions follow the regular F1 weekend pattern, but moved back to begin with practice one at 2pm local time.
That makes it and Saturday's 3pm local time practice three a complete contrast to the cooler sunset conditions of practice two, qualifying and the race.
Hamilton says scorching heat during first practice this Friday meant there was nothing to learn from the session, as he believes the tyres are not suited to running in such conditions.
"It's always weird," he said of the Bahrain practice one time.
"It's at the worst time of day, because it's so hot, 60-degree track [temperature], it's kind of a waste of a session really.
"It's so hard on the car, it's not a problem for us drivers but it's tough on the tyres.
"It's horrible to drive, it's not fun, the tyres are melting and you're sliding around with no grip.
"You put a chocolate bar on the track, it would melt in a minute and that's what it's like for the tyres.
"You don't really learn anything, because then you go into FP2 and it's completely different."
Haas driver Kevin Magnussen echoed Hamilton's sentiment.
"[It] is extremely hot and the tyres don't behave very well," he said of the daylight session.
"It's difficult to do any laps, also because the brakes, engine, gearbox, everything overheats.
"You can only do one lap and then you have to cool down."
All three evening F1 races feature two practice sessions in daylight, with the same timetable format applied in Singapore and Abu Dhabi.
MotoGP swaps its timetable to a four-day format for its Middle Eastern night race in Qatar, spreading the main practice sessions across Thursday and Friday evenings so all can take place in the same after-dark conditions as the grand prix.