President Uhuru Kenyatta is expected to attend the ceremony, scheduled to start at 9 am.
Police say those invited there should be seated in time because of other security plans. More security personnel have been deployed there to guide the arrival of the guests.
Last week, Sonko rejected the Sh25 million shillings meant for the inauguration.
He instead directed that the monies be used to offset salary arrears owed to county employees.
Frequent withdrawal of services by contractors due to unpaid fees has contributed to the mismanagement of garbage in the city, a report revealed in January.
On Tuesday, Sonko assured contractors and suppliers that pending payments will be cleared as soon as he is sworn into office.
In a gazette notice, Sonko cautioned them from being duped by fraudsters who are reportedly soliciting for bribes to facilitate speedy processing of their payments.
“I wish to categorically state here that I have not mandated anyone whatsoever to either solicit or follow up on any pending payment at City Hall,” Sonko said.
President Uhuru on Saturday met with Nairobi Jubilee elected leaders and urged them to avoid squabbles when they assume office.
-The Star