Good Friday is the traditional day of Jesus crucifixion. It takes place on the Friday afternoon before the Passover.

Passover Timing

The Passover was one of the most important holy days to the Jews. It is one of the Spring Feasts.

But that doesn't really say enough. The Passover was the first feast of the year. The year was ordained to start at this time by God in Egypt at the time of the exodus.

Exodus 12:2

This month shall be for you the beginning of months. It shall be the first month of the year for you.

This month is called Abib, or Nisan.

“Abib” is the month in the spring when the first-fruits of the barley harvest had to be offered up on the second day of Passover, or Abib (or Nisan) 16, to the Lord (Lev.23:10-11).

“Nisan” itself is another name for this month. “Nisan” in the Hebrew, denotes “the month of flowers” (Gesenius Hebrew-Caldee Lexicon of the Old Testament, #5212). 1

The Jewish calendar was lunar (moon) and solar (sun) based, but a lunar year is slightly off from a solar year/cycle.2 Lunar months are shorter than solar months. Without adjustment, a lunar year would slowly shift around the months of the calendar we use now so the year would start earlier and earlier eventually making this spring feast happen in the (weather based) season of winter.

The Jewish calendar system knew this and had a solution to fix it. To account for this shifting of the calendar, the priests would take note of the solar equinox and the weather in anticipation of the new moon and if the equinox was not going to land near enough 3 and the weather was not ready for a new year to begin (with spring) the court would intercalate an extra month. Now when the next new moon came it would be in spring. This intercalation was done by physical observance of the moon at the time of Christ. Now it is arrived at through calculation so as to allow the dispersed Jews to celebrate it together worldwide without communication or decree.

Impact of this timing

Passover in winter would be very bad. Before the Passover, basically the entire nation of Israel came to Jerusalem for the sacrifice. For that many people to travel, to find lodging, and to have food, it requires a lot of preparation. They would need time to prepare the roads, the food, and the lambs for Passover.

Speaking of the lambs, they needed to be one year old lambs. Lambs are born in later winter and early spring, so they would be at one year at the start of spring. 4

So you see, it was not only important that the Passover be in spring, it was practically necessary.

Why would Peter be cold?

However, back to Peter, it was most likely still cool in the early morning. And we know it was around dawn because, well, that's when roosters crow.

At the time of this writing it is an unseasonably warm March day for the East Coast in the United States, but I still put on a hoodie when I left for work before dawn. I even spent a moment in front of the heater at work.

Conclusion

So we see, by its very definition, the Passover must be on the 15th day of the first month of the new year, which cannot begin before spring.

Therefore the first "Good Friday" must have been in the spring, when it was still a bit cool at night and early in the morning. For Peter to be warming himself by a fire at that time is not unusual.

I hesitate to answer a question with an already accepted answer, especially one which agrees with my own answer. However, I felt no answer provided enough background information beyond simply stating the answer, with no explanation or sources. So this is my attempt to provide that to any future readers.