One of the big draws on the Maes is the Open Art Exhibition.
Fifty-six artists have been chosen this year to show their work - and nearly half of them are taking part in the Eisteddfod for the first time.
Carole Green caught up with one of the newcomers.
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The heaviest bursts are expected in the south and east, with some western areas either remaining dry or becoming dry by dawn.
Many places will start dry, but rain in the southeast will spread to most for a time overnight.
The family of Isaac Nash who went missing after being swept out to sea last summer have presented a cheque for £10,000 to the RNLI.