At what temperature does water boil at 1000 metres asl? How long should I boil a "5minute"at sealevel egg?

Question

I live close to sealevel; usually a 5 minute soft boiled egg is just fine, but when I am 1000 metres over sealevel, it is very runny. I realise that the water boils at a lower temperature at altitiude, but how much lower and how much longer should I leave it to boil?

Answer 1

At an altitude of 1000 meters the boiling point of water is little changed from that at sea level - it's 96.7 degrees Centigrade (206.1 degrees Farenheit). The difference it will have on your egg is minimal and you'll only need to boil it for a few seconds more.

Answer 2

altitude (metric) 1000 m
altitude (imperial) 3280.8 ft
air pressure 88.717% % 1atm
air pressure 90.042

Adjustment for 3000+ feet:

Reduce baking powder:
For each tsp., decrease 1/8 tsp.

Reduce sugar:
For each cup, decrease 0 to 1 Tbsp.

Increase liquid:
For each cup, add 1 to 2 Tbsp.

expect rice cooked at 5,000 feet (1,500 meters) to take 25-30 minutes instead of 20-25 minutes of simmering before the water is absorbed and the rice is done.

How about that egg we want to cook on top of a high mountain, say at 10,000 feet?
We now know that the water will boil at a lower temperature on top of the mountain at lets say, 185 degrees Fahrenheit. To hard-boil an egg at sea level takes say, five minutes at 212 degrees Fahrenheit.

Now, there is a very good law in chemistry that states "You cannot get something for nothing" (the left-hand value of an equation must equal the right-hand value). Time multiplied by temperature equals a hardboiled egg. That is to say, 212 times 5 equals a hardboiled egg.

If the temperature of the boiling water on the mountaintop is 185 degrees Fahrenheit, then the time taken to cook the egg will have to INCREASE to get our hardboiled egg. Our equation to equal a hardboiled egg cannot change. (185 times extended time equals hardboiled egg.) It is no different to cooking a piece of steak or cooking the potatoes. You can cook at a low temperature for a long time, or a high temperature for a short time.

It is time and temperature that does the cooking. It has nothing to do with whether the water is boiling. That is only a physical phenomenon that you can see. You have to measure for temperature and time, as these are the two factors that determine when the egg is hardboiled.