“First, we’re living in a high dry climate, one mile or more above the sea: so foods boil quicker but need to cook longer. The dry air can play tricks on you. Remember to seal everything moist of course; but, also remember that when cooking by direct heat (broiling) you’ll need to adjust the food a bit farther away than you do in a moist climate to assure the same degree of doneness. Also, your favorite cake recipes will probably need some adjusting.”

Here is more:
Water boils at 202 degrees at 5000 feet and 198 degrees at 7000 feet meaning that you will need to cook everything longer. This is because the food is cooking at a lower temperature.

Cook candies to a lower temperature than stated in sea level recipes to coompensate for faster evaporation. The rule is lower the temperature one degreee for each 500 feet of altitude. We recommend that you do not use the candy thermometer alone, as cold water tests are more accurate and should be done even if a thermometer is used.

Deepfat Frying:Lower the temperature about 2 to 3 degrees for each 1000 feet of altitude or about 10-15 degrees for 5000 feet and 14-21 degrees for 7000 feet.

Canning: Increase the processing time for the water bath method one minute for each 1000 feet elevation if the processing time is 20 minutes or less. Increase the processing timme 2 minutes for each 1000 feet above sea level if the processing time is more than 20 minutes.
For pressure canning, increase the gauge pressure ordinarily used one pound for each 2000 feet above sea level.

Good Luck!