In Test cricket, play cannot start, is immediately suspended, or cannot restart if the on-field umpires agree the light conditions are "dangerous or unreasonable".
That wording comes from section 2.8 of the International Cricket Council's Test match playing conditions, which states the decision on whether lighting is unsafe is solely down to the umpires, following consultation with the ICC match referee.
Umpires are allowed to use light meters, which must be supplied by the ICC, as a guideline to determine whether light is fit for play or is improving or deteriorating. Light meters must be uniformly calibrated.
When natural light has worsened to a level deemed unfit for play, the umpires will authorise the 'ground authority' – those responsible for hosting the match – to use any available artificial lighting so play is able to continue in acceptable conditions.
Should artificial lighting at the ground not work, rules on natural lighting and weather will apply.
For day/night Test matches, the home cricket board will decide the latest times at which the floodlights are to be switched on prior to the start of a day's play, and must inform the match referee.
Once play is suspended, it is the responsibility of the match umpires to continue to monitor conditions.
This article is the latest from BBC Sport's Ask Me Anything team.
Send us your questions
Ask Me Anything is a service dedicated to answering your questions.
We want to reward your time by telling you things you do not know and reminding you of things you do.
The team will find out everything you need to know and be able to call upon a network of contacts including our experts and pundits.
We will be answering your questions from the heart of the BBC Sport newsroom, and going behind the scenes at some of the world's biggest sporting events.
Our coverage will span the BBC Sport website, app, social media and YouTube accounts, plus BBC TV and radio.
What is umpire's call in cricket?
Why isn't cricket played in the rain?
What is a demerit point in cricket?
How do points work in the County Championship?
India middle order frustrates England after Archer's early strike
Ringrose withdraws after being named in Lions side
Transfer news: Ekitike joins up with Liverpool squad; Wolves sign forward Arias
Inside the homes of three men who changed British life
Investigating the rise of medical conspiracy theories
Do estate agents treat customers fairly?
The extraordinary life and legacy of author Alexandre Dumas
Bonmati winner sends Spain to Euro 2025 final – highlights. Video
We meet again – England & Spain set for 'amazing' Euro 2025 final
'Understated and intimate' – the view from Rashford unveiling
'Greatest stadium on earth' – Lions set for debut at The 'G
Is it time for injury replacements in Test cricket?
Kelly's extra-time goal gives England victory over Italy Video
Should Agyemang & Kelly start Euros final?
Prem season to open with first Thursday night game
Are Aston Martin dark horses to sign Verstappen?
Harmanpreet and Goud star as India beat England to secure ODI series. Video
'Historic' football regulator bill becomes law – what it means for fans
What made playing with Bumrah unique – Pujara column
'Toppling Scheffler becomes the next objective for McIlroy'
'He did things-no one could do' – how 2005 Ashes 'reinvented' Flintoff. Video
'We felt like Premier League footballers' – Jones relives 2005 Ashes
Diogo Jota: A tribute. Video
Copyright © 2025 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.
Cricket: What are the rules about bad light in Test matches? – BBC
Related articles
