potted bulbs starting too early
Doug says the only way to stop them from growing is to get them colder. Your porch is obviously a warm porch. (although you don't say where you are)
Why are they coming out now -because they think it's spring.
Slowing them down- get them colder.
Will the cold kill them - not likely but it depends on how cold you consider "cold". Minus 40 should do some serious damage -but 32F shouldn't.
Bring them indoors? If you want to beat all the neighbors with flowers this season - goferit :-)
Leaving them outdoors will slow them down and the colder weather will keep them growing slowly. Bringing them indoors is going to get them growing quickly.
It all depends if you want to see the blooms now or wait for ?? :-)
All the best.