If it's for me, I will leave them in the basement, give them suffiecient water and lighting. That's what I did with my lilies bought too early in the season and with long sprouts too. They are already blooming. My basement temp is probably the same as yours. Although mine are planted in a bigger pot.

Why do you think it is too early to plant them outside? Do you expect hard frosts? Lilies are perennial in your zone. The top growth can tolerate light frost (above 28F).
If you keep them potted, it is perfectly OK to put them outside. If you will have frosts, bring them inside for a night. No need to take them inside for a wet weather provided your pots have good drainage.
Lilies are not indoor plants. They will not do well in the darkness even for a short period of time.

Hi,
I bought the same bulbs at the start of March. The sooner you get them out of the store the better because they only start growing there where it is warm. I tried keeping them in the fruit cellar in Wood shavings where it was cool and dark but some of them( mostly the Asiatics) started to grow anyways. I potted up the ones that were and put them outside on my deck. The others I put in the fridge. I live in Ontario Zone 5a. There have been a few frosty nights that I have brought them into the garage but for the most part they have been outside. Most are only about 1-2" tall yet but the cool weather has held them back. Make sure your pots get enought sun or they will reach for it. I have put some that I was ready for into the garden and have some that I ordered by mail order coming this week. They will go right in the ground. Lilies can handle cool weather. I have many planted in the gardens emerging so it must be the right time for them to come up.
I would put yours outside to slow them down a bit, give them lots of light and just watch the thermometer.
Debbie