The Gemara (Berachos 34b) writes that it is wrong (arrogant — chatzuf) to daven in an open field.
Rashi explains that in an open field, one doesn’t feel fear of the
King, and one doesn’t pray with a broken heart. Tosafos, however,
understands that the concern is for passers-by, who are liable to
disturb a person’s davening.
The Magen Avraham (90:6) rules that the problem is that davening
outside makes a haughty statement: “Even though there are passers-by,
they will not disturb my intent in davening!” This is arrogant and
The Shulchan Aruch (90:5) rules that one should not daven in an open
place, and the Mishnah Berurah (11) adds that those who are always
traveling can daven in an open place, but should try to daven
by a tree.
Therefore, although it is not forbidden to daven outdoors, it is wrong
to daven in an open area, and one should seek a sheltered place.
Additional details are brought here:
Level of Priority
Pri Megadim/ Mishnah Brurah (90:10): If a person had a choice between
davening in a house with no windows or outside he should daven in the
house. Davening with windows is a nice mailah whereas davening in a
wide open area is an issur.
An Area With Walls But No Roof
Sharei T’shuvah (90:1): He brings a string of poskim who all agreed
that an area with walls is enough to meat the requirements of this
Gemara even though it has no roof!
Magen Avraham (90:6)/ Mishnah Brurah (90:11): A traveler who is in a
hurry and must daven on the side of the road may do so. There is no
chutzpah involved here since this person has no choice but to daven
where he is.
Chayeh Adam/ Pri Megadim / Mishnah Brurah (90:11): Even for a traveler
it is preferable to find a semi-secluded place (i.e. amongst some