As long as the bulbs are in good condition, it is never "too late"....they will keep much better in the ground than stored on a shelf :-) But they probably won't bloom if planted now. They need at least 12-16 weeks of cold below 40F to initiate healthy growth and flowering. I'd also question whether or not you need to plant prechilled bulbs as well. In many more southerly locations, that is a requirement to achieve the necessary chill hours, even when planted at a more typical late fall schedule.