For fans of George RR Martin, winter is not coming – at least not right away.

The Game of Thrones author says he missed a December 31 deadline to finish The Winds of Winter, the sixth book in his popular fantasy series.

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That means the next HBO season based on the novel will start airing in April, before the book is published.

The words “you won’t like it” appeared Saturday on Martin’s blog, reporting that “the book’s not done. … I tried, I promise you. I failed.”

Martin says he is working with HBO to ensure the show reflects the next instalment of the A Song of Ice and Fire books – in which characters warn of impending doom with the phrase “winter is coming”.

With hundreds of pages and dozens of chapters written, Martin said he estimates it will still take months more if the writing goes well.

“You can blame my travels or my blog posts or the distractions of other projects and the Cocteau and whatever, but maybe all that had an impact,” he wrote, referring to the single-screen Jean Cocteau Cinema he purchased and fixed up in Santa Fe, New Mexico, where he lives.

“For months now I have wanted nothing so much as to be able to say, ‘I have completed and delivered The Winds of Winter’ on or before the last day of 2015,” the 67-year-old author blogged.

The truth is “sometimes the writing goes well and sometimes it doesn’t, and that was true for me even when I was in my 20s,” he wrote.