Heavy traffic is also reported in the roads of the sacred city of Anuradhapura and the way towards Mihintale, reports from Anuradhapura say.
A 4000 strong police force and Army are deployed for the security of the city, police say.
Special lifesaving squads of Navy have also been stationed near the reservoirs, According to the organizers.
A large number of Pandals, lanterns and other Buddhist decorations are in display around the country while lot of Dansalas (alms offering places) are also visible.
A team of 100 Public Health Inspectors has been deployed to inspect the Dansalas and restaurants within the Anuradhapura Sacred City and the suburbs. Dansal and restaurants as well as drinking water will be subject to thorough checks.
Meanwhile the state Poson festival is held in Sithulpawwa in the Hambanthota district of the Southern Province.
Elsewhere in the country Speaker Chamal Rajapaksa ceremoniously laid the foundation for the 2nd phase of construction of a pilgrims rest and a Wahal-Kada (gate) at the Tissamaharama Raja Maha Viharaya this morning.
The annual Ruhunu Maha Poson Perahera of the Tissamaharama Raja Maha Viharaya is scheduled to parade the streets tonight.
Large crowds gathered at most of the historical places of Buddhist worship in the country to observe percepts (Sil) and conduct religious activities.
The depositing of sacred relics at the Samadhi Buddha Statue in Mahiyangana Viharaya took place this morning. It is the largest Samadhi Buddha Statue constructed in Sri Lanka to coincide with the 2600 Sri Sambuddathwa Jayanthi.
Political sources say the people are increasingly enjoying the benefits of peace achieved after the defeat of the Tamil Tiger rebels in 2009.