it is said that plants know the weather long before it happens.  now we have science, so to see what it is they know.  here is 2016 air temps so far, and last year 2015.  notice the white (colder than 2015) upper air is warming up fast (er than 2015).  my prediction, summer will be here by march.  there may be another burst of upper cold or two before then, weather is never predictable, only observable.