Thanks for all the answers. I have an Oasis humidifier that I can hang on the strings.
One of these:
http://www.oasishumidifiers.com/plus.html
Are these any good? Should I use it now? Is there a chance that the humdifier will break and I will get water in my guitar? It says on the package that I should use distilled water. Is it fine to use regular water? The water in Sweden is really clean and good.