A unit used in expressing the extent of cloud cover, equal to one eighth of the sky.
- ‘The amount of sky covered is typically measured in oktas, eighths of sky cover, a non-linear scale.’
- ‘It was 0.2 + / 0.06 (54% of clear sky conditions) for activities in which cloud cover was measured at 7 okta or greater.’
- ‘Overcast skies (typically 7-8 okta of stratus) reduced exposures by a mean of 54%.’
1950s: alteration of octa-.