ABIDJAN, May 10 (Reuters) - Below average rainfall and hot weather last week in most of Ivory Coast's cocoa-growing regions could reduce the quality and size of the April-to-September mid-crop, farmers said on Monday.

Ivory Coast, the world's top cocoa producer, is in its rainy season, which runs from April to mid-November. But rainfall has been irregular in the last two weeks and farmers said beans could be small and acidic by June and July if the conditions persist.

In the centre-western region of Daloa, which produces a quarter of national output, farmers said the harvest could end early unless the weather changes.

"The prolonged absence of good rains is starting to worry us. There are lots of small pods which could dry out and fall from the trees," said Albert N'Zue, who farms near Daloa, where rainfall was recorded at 4.9 millimetres (mm) last week, 19.1 mm below the five-year average.

In the central regions of Yamoussoukro and Bongouanou, farmers said the lack of moisture could reduce bean quality.

"If the rains don't come fast our beans will be rejected around mid-June and July for high acidity," said Jules Assemian, who farms near Yamoussoukro, where 17.2 mm fell last week, 7.7 mm below the average.

Rains were also well below average in the western region of Soubre, at the heart of the cocoa belt, in the southern regions of Divo and Agboville and in the eastern region of Abengourou.

"It is time for heavy rain or else the beans will be small and of bad quality," said Salame Kone, who farms near Soubre, where 3.3 mm fell last week, 28.4 mm below the average.

Average daily temperatures ranged from 26.7 degrees Celsius (80.06°F) to 30.9C last week. (Reporting by Loucoumane Coulibaly; Editing by Nellie Peyton and Barbara Lewis)