When training outside in the winter (20 30F) my max HR seems to be 3 - 4 BPM lower than in warm weather. My ability to do long rides in high Zone 4 seems to be more difficult also. Does anyone else find this occurs with them also?

When training outside in the winter (20 30F) my max HR seems to be 3 - 4 BPM lower than in warm weather. My ability to do long rides in high Zone 4 seems to be more difficult also. Does anyone else find this occurs with them also?
and any type of hard efforts the legs seem a bit blahhhh while I'm doing them.

When training outside in the winter (20 30F) my max HR seems to be 3 - 4 BPM lower than in warm weather. My ability to do long rides in high Zone 4 seems to be more difficult also. Does anyone else find this occurs with them also?

I think it's because your heart is working harder in the summer to keep you cool as well as feeding muscles.