Nominations are now open for this year's Hugo awards. You can nominate if you are a member of last year's Worldcon, this year's Worldcon, or next year's Worldcon, as of January 31 this year.
In other words, if you want to nominate and you're not a member of any of those Worldcons, you have until January 31 to buy a membership (supporting or attending).
I urge anyone who is interested in the Hugos to nominate. The nominations process is how the Rabid Puppies have controlled the Hugo ballot for the past couple of years, and I see no reason to think they won't try again this year. There are new systems in place to dilute the impact of their slate, but those systems likely won't help as much as we had originally hoped they would. So please nominate if you can. You don't need to be an expert or to have read everything published in 2016; all you need is $40 US and an opinion about some works you like. (And being a member this year also lets you nominate next year.)
IIrc, a large majority of Worldcon members each year do not nominate even though they can. If you're already a Worldcon member, please consider participating in the process. If there was even one work published in 2016 that you liked, you can nominate it.