A multi-faith prayer and release of doves is due to take place at 09:15 BST.
Organisers are encouraging attendees to wear or accessorise in "green for Grenfell" in a display of "reverence and respect amidst the revelry".
A "ring of care" will be formed around the tower by police.
More than 80 people are believed to have died when fire engulfed the Grenfell Tower block of flats on 14 June. The carnival route passes near the tower.
Pepe Francis, chairman of the carnival trust, said: "We support the suggestions of the local community and wider carnival community to start this year's carnival earlier.
"This will be the first opportunity for visitors to carnival to pay their respects for those affected by Grenfell."
Hundreds of hand-drawn tributes, flowers and candles will be protected by fencing, while the public have been asked not to take selfies at the site.
A reflection zone will be placed near the burnt high-rise, where performers will lower the volume of their music.
MP Emma Dent Coad, who likened the carnival to a wake, will give a speech ahead of the dove release.
At 15:00 on both days, hundreds of thousands of revellers along the route are expected to pause and observe a minute's silence to mark the tragedy.
A spokesman for Grenfell United, a residents and survivors group, said: "We hope people will follow these requests from us and our friends and family in the wider community.
"They will enable people to pay their respects; be conscious of our vulnerability; and show solidarity for our ongoing demands for housing and full justice, in the creative spirit of carnival."
Steel barriers, concrete blocks and a ban on vehicles will be in place to protect revellers from the threat of terrorism.
Scotland Yard said there was no specific intelligence but security plans had been "thoroughly reviewed" after the Barcelona attack.
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Angela Reakes, 24, of the ACT Meteors in the Women's National Cricket League, was guilty of breaching Cricket Australia's (CA) anti-corruption code.
She pleaded guilty to placing five bets on the Australia v New Zealand final man-of-the-match betting market.
CA integrity unit chief Iain Roy said: "Angela knows she made a bad mistake."
He added: "All elite cricketers are reminded regularly that betting on any form of cricket is strictly prohibited."
Australia won the World Cup final in March, beating New Zealand, with James Faulkner named man-of-the-match.

Geoffrey Sutcliffe admitted causing the death of Lucille Abraham, 92.
When applying to renew his driving licence, a court heard, Sutcliffe said he met the "required eyesight standard" and did not need glasses to drive.
He was sentenced to eight months in prison, suspended for two years.
Sutcliffe hit Ms Abraham, from Baildon, at the junction of Godwin Street and Kirkgate, in Bradford, last October.
During an eye test the previous month, Prosecutor Michael Smith said, Sutcliffe told the optometrist he was not a driver.
Had he done so, Mr Smith said, she would have said that his eyesight had failed the visual acuity test.
"The defendant suffers from cataracts in both eyes and it seems that the medical opinion here is that he should not undergo an operation on his right eye because effectively that's the only eye that can see," said Mr Smith.
Barrister Ken Green, for Sutcliffe, said he had been driving for over 60 years without any previous offending and his client intended never to drive again and had surrendered his licence.
"He will never forget that day and I am sure he will never forgive himself for that error that he made," said Mr Green.
Passing sentence, Judge Colin Burn said "It is obvious that you should not, with the benefit of hindsight, have been driving at all on that day.
"Your eyesight wasn't up to it as a matter of objective fact."
He added: "The misrepresentation you made about your eyesight was a contributory cause of this collision because you shouldn't have been driving at all."
Notting Hill Carnival will open with a special ceremony as a "small act of remembrance" following the Grenfell fire tragedy.
[NEXT_CONCEPT]
An Australian cricketer has received a two-year suspended sentence for bets totalling Aus $9 (£4.36) during the 2015 Cricket World Cup.
[NEXT_CONCEPT]
An 81-year-old driver whose poor eyesight meant he should not be on the road has been given a suspended jail sentence after he hit and killed a woman.