If it was intended to bloom at Christmas, then must have been pre-chilled and forced. Forced bulbs are not the easiest to generate further blooms from and even under the best condtions will take a season or two to buld up steam and rebloom on a normal schedule and in the traditional setting. If forced in water (as opposed to a potting medium), it is very unlikely to rebloom and best just to toss. Either case you are not likely to see blooms on it soon, certainly not this summer.

Funny the impression one develops about places they have never been - I would never have thought Iceland would be a zone 5, although I do know you can have some extraordinarily lovely gardens there.

Hyacinths don't bloom in summer, they bloom in spring. If you plant it in the garden, it will go dormant and then sprout next spring. Naturalised Hyacinths have less densely packed flower stalks but they are hardy and they last for years. Don't spread much though.

Just keep it watered with a little fertilizer from time to time - in a sunny window. Plant outside in spring after the weather settles. It won't bloom again this year but will do fine next year. I have lots of hyacinths in the garden that all started as forced plants. Typically they have a loose inflorescence the first time they bloom outside but they build up the bulb from year to year and will eventually have the tight cluster of florets typical of hyacinths.
You can also do this with forced daffodils (NOT paperwhites) and some other spring bulbs, but not tulips.