Extreme spectra are a subset of the ensemble of climatic wave spectra corresponding to severe storm conditions in a sea with the certain return period. There are at least five classes of climatic spectra in the World Ocean, namely: wind waves, swell, wind waves and young swell, matured swell and wind waves, complicated wave fields. The parameters of climatic spectra and extreme spectra are describing by means of their joint distribution. The approach to design the extreme wave spectra is developed and partly realized in the new generation of wind and wave handbooks published by Russian Maritime Register of Shipping. Particularly, for Japan, Kara, Bering and White Seas climatic directional wave spectra (for return periods up to 100 years) are calculated.