In a case of extenuating circumstances, one may recite Birkot Keriat Shema from the time of amud hashachar, which is 72 minutes before sunrise (in the months of Nisan and Tishrei).1 However, as long as it is possible to recite Birkot Keriat Shema after the time of misheyakir, one may not recite them from amud hashachar. For instance, if someone who is traveling can pray while walking or sitting (as his friend drives), he must wait for the time of misheyakir and only then recite Birkot Keriat Shema and recite the Amidah while walking or sitting.
If he is able to recite Birkot Keriat Shema while he is traveling after the time of misheyakir, but cannot recite the Amidah while traveling, he should pray the Amidah earlier after amud hashachar and recite Birkot Keriat Shema and Shema while traveling, even though he will not merit connecting redemption to prayer.
When it is not possible to recite Birkot Keriat Shema while traveling, as, for example, if he does not know Birkot Keriat Shema by heart, and it is not possible for him to use a siddur, he may pray earlier since such situations are considered extenuating circumstances. He recites Birkot HaShachar, Korbanot, and Pesukei d’Zimrah before amud hashachar, and when the time of amud hashachar arrives, he puts on his tallit and tefillin without a berachah, recites Keriat Shema and its berachot, and prays the Amidah. When he finishes the Amidah, the time of misheyakir will have already arrived, and at that point he takes hold of his tzitzit and tefillin and recites the blessings upon them. According to the Ashkenazic minhag, Birkat Yotzer HaMeorot may not be recited before the time of misheyakir either; rather, one must delay its recital until after praying the Amidah.
. In Berachot 30a we learn to what extent reciting Keriat Shema and its berachot before misheyakir is only for extenuating circumstances, since any time it is possible to say them after misheyakir, even while walking, there is an obligation to do so. The only question left is when to pray the Amidah. According to Rabbeinu Chananel, the Tosafot, and others, one must recite the Amidah standing in his house before misheyakir, which is how the Shulchan Aruch 89:8 rules as well. According to Bahag, it is best that he prays while walking so as to connect redemption to prayer, and in practice, that is customarily what is done, as explained in the Mishnah Berurah 89:42 and Kaf HaChaim 54. However, when he can say Birkot Keriat Shema while traveling, but cannot pray the Amidah, then he follows Rabbeinu Chananel and the Shulchan Aruch; he prays the Amidah standing in his house after amud hashachar and waits to recite Birkot Keriat Shema while traveling in order to say them after the time of misheyakir. This includes a case in which a person only knows the berachot of Keriat Shema by heart and not the Amidah, or one in which a person is driving and he knows that he is capable of reciting Birkot Keriat Shema while driving, but praying the Amidah while driving is forbidden (see further in this book 17:16).
.During the days of Nisan and Tishrei, amud hashachar is 72 minutes before netz (when the sun is 16.1 degrees below the horizon). In the height of winter (December 22nd) it is 78 minutes before netz, and at the height of summer (June 22nd) it is 88 minutes before netz. See note 1 to understand why I have written according to this opinion. At most, it is permissible to be lenient and consider amud hashachar the first light in the east (when the sun is 17.5 degrees below the horizon), as explained there. Many calendars display amud hashachar as a time when there is no light at all in the eastern sky, and it is very problematic to rely on them.
In note 2, I wrote that the time of misheyakir is when the sun is 11 degrees below the horizon, which is the average time according to the different opinions and observations. However, here, in extenuating circumstances, if one can recite Birkot Keriat Shema approximately five minutes before this time, thereby succeeding to pray the Amidah standing in his house, it is preferable that he does so, instead of praying afterwards while walking.
In a case of extenuating circumstances, it is permissible to start praying Birkot Keriat Shema from amud hashachar, as explained in Shulchan Aruch 58:3. One may put on his tallit and tefillin before that time without a berachah, as clarified concerning the matter of tzitzit in Shulchan Aruch 18:3 and Mishnah Berurah 10 and regarding the matter of tefillin in Shulchan Aruch 30:3 and Mishnah Berurah 11. However, Kaf HaChaim 30:8, based on the Ari, writes that one may not put on tefillin before amud hashachar. Additionally, it is explained in Shulchan Aruch 1:6 and 47:13 that the passage regarding the Tamid may not be recited before amud hashachar and, according to Kaf HaChaim 89:7, Pesukei d’Zimrah may not be recited before amud hashachar either. However, we have already learned that some poskim maintain that amud hashachar is slightly before the time mentioned above and others say it is 90 minutes before netz, as written in Kaf HaChaim 89:1. In extenuating circumstances, with regard to these matters, in which there is no issue of reciting a berachah in vain, it is permissible to rely on this approach.
According to many Ashkenazic poskim, Birkat Yotzer HaMeorot may not be recited before misheyakir. So write the Magen Avraham, Graz 58:6, and Mishnah Berurah 58:17. Nevertheless, if a person did recite Yotzer HaMeorot before misheyakir, since he already fulfilled his obligation according to the Shulchan Aruch and Kaf HaChaim 58:19, he does not repeat it again after praying (Bei’ur Halachah 58:4, s.v. “B’lo”).