Tulips

I planted some tulip bulbs in my front garden I don't know how many years ago.  At least 5.  They were planted in the expectation that they would perform as annuals, because tulips don't do so well in our warmer climate.  Yet here they are, multiplying and flowering year after year after year.  It seems to me that our nights are getting colder, or maybe that's just me getting older.  Whatever, it seems to work for these bulbs.