moving from trainer to road- HR increase...

I've trained on a trainer and/or spin bike A LOT (for me)  this winter. Because I often go at lunch time, my sessions haven't been long (35-45 minutes) but I've trained 4-5 times a week, sometimes 6x. As I got more fit, I found it harder to get my HR above 100, but I'd increase resistance or cadence and would usually ride about 112-116 bpm gradually riding in the 124-130 range, with the average being low 120's.   Saturday I did my first outdoor ride in months, and found my HR above 130 almost immediately, maybe 5 minutes in to the ride.  It was relatively flat terrain, but with a decent headwind, riding big ring (53) in the front, and somewhere around 15-17 ring in the back, low 80's cadence.  I slowed down and decreased resistance and ended up with an average of 128 for about 90 minutes. Still I'd have thought my HR would have been much lower, especially to start out.  I'm thinking maybe my resistance on the trainer might be too low, thus my indoor rides are not similar enough to real ring.   Has anyone experienced this?