2,811. When Is Summer?
Hilchos Nedarim 10:9
If someone prohibits something to himself until the summer, he is prohibited until the people of his locale start bringing in baskets of figs. If until the harvest, then he’s prohibited until people harvest wheat, not barley. If he says, “until summer passes,” he is prohibited until most people fold up the mats that they designated for drying figs and grapes. It all depends on the local practice of the locale in which the vow was made.
Hilchos Nedarim 10:10
Pursuant to the previous halacha, if one made a vow in a valley and prohibited something upon himself until the summer, after which he moved to the mountains, he may not rely upon whether or not the fig harvest has started in his new locale. Rather, it all depends on the place where he took the vow. The same applies in such cases.