Lot's Twilight Escape

There is a dispute in the Gemara as to the length of halachic twilight in the morning hours. One opinion mentions that this is a 4 mil time interval and the other states 5. As a proof to the opinion of 5 the Gemara cites from this week's parsha when Lot was escorted out of Sedom in the early hours of the morning. The Gemara maintains that he traversed a 5 mil distance in the exact amount of time between dawn and sunrise. (See Pesachim 93b)

Although this proof is ultimately rejected because it seems that Lot was rushing and the Gemara is referring to people traveling at an average pace, it seems that barring this point that the Gemara would have been content with this proof. The question one may ask is that twilight periods vary based on latitude and also based on the time of the year. How did the Gemara know that the case of Lot was a good proof, perhaps, it happened in a location other than the one the Gemara was discussing, or at a time of year different from the one in the Gemara?

The Gemara's discussion was regarding Korbon Pesach, so we can deduce that the location of its discussion is in Eretz Yisrael. We can also deduce that the time of year it was discussing was at the beginning of spring since that is when Pesach falls. How did the Gemara know that Lot's escape was at this time and location?

Regarding the location, the Gemara easily knew that Lot's escape was in Eretz Yisrael because it happened in Sedom. The Gemara also seems to be of the opinion of the Bereishis Rabbah regarding the time of Lot's escape. Bereishis Rabbah maintains that it happened on the second day of Pesach. (Bereishis Rabbah 48:12) In fact, Rashi also mentions the fact that it was on Pesach. (Rashi Bereishis 19:3) So, with these facts being presented one can clearly see that had it not been for the fact that Lot was running for his life, the Gemara would have had an adequate proof.