Poor Husband's Problem

After his exam the doctor asks his elderly patient, 'You appear to be
in good health.
 Do you have any medical concerns you would like to ask me about?'
'In fact I do,' says the old man.
'After I have sex with my wife, I am usually hot and sweaty, and then,
after I have it with her the second time,
 I am usually cold and shivery.'
The doctor then examines his elderly wife, then asks her, 'Everything
appears to be fine.
 Do you have any medical concerns that you would like to discuss with me?'

The lady replies that she has no questions or concerns.
The doctor then asks her,
'Your husband has an unusual concern.
He claims that he is usually hot and sweaty after having sex with you
the first time, and then cold and shivery after the second time.

Do you have any idea why that may be so?'
'Oh that!' she exclaims.
'That's because the first time is usually in July and the second time
is in January!'