I believe you are correct about late cold snaps. They were particularly detrimental in Vertisols soil of Blackland Prairie. The choice weapon on these expansive soils is a water hose for unseasonable heat or cold.

My water lilies, especially my Wanvisa hasn't bloomed yet and it typically starts in mid-April. On the other hand, my Gregg's Mistflower and Joe Pye weed are already blooming. It's a weird year for sure.

Yes this hasn't been a typical year fot sure. A while back my neighbor asked why his lot wasn't covered in yellow flowers as it normally is. I told him to be patient, sooner or later Dandelions ALWAYS make their appearance.