It would hardly do for this thread to pass without some pedant pointing out the extreme poetic licence which Ms. Rosetti saw fit to indulge in when penning the first stanza:

In the bleak midwinter,
frosty wind made moan,
earth stood hard as iron,
water like a stone;
snow had fallen, snow on snow,
snow on snow,
in the bleak midwinter,
long ago.

I have just checked the weather forecast for Bethlehem (Israel, not PA) and the temperature tomorrow is expected to reach 21 degrees Celsius (70 degrees Fahrenheit)

Is there any reason to suppose that the climate was any different in December between 1 BC and 1 AD ?

I don't think we need to sympathise retrospectively with Baby Jesus an account of his nursery conditions, temperature-wise at any rate ...