'If you look out the window' vs 'If you look out of the window'

English as a Second Language English Teacher Explanations (ESL Tests)
1

English Grammar Tests, Elementary Level

ESL/EFL Test #114 [color=blue]“Weather Test (1)”, question 7

If you look out the window and it’s snowing, it’s probably … outside.

(a) cool
(b) warm
(c) cold

English Grammar Tests, Elementary Level

ESL/EFL Test #114 [color=blue]“Weather Test (1)”, answer 7

If you look out the window and it’s snowing, it’s probably cold outside.

Correct answer: (c) cold

Your answer was: [color=green]correct
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Shouldn’t it be:
If you look out of the window…
with added ‘‘of’’?

2

.
‘Of’ is optional here.
.

3

why we can’t say : “It is cool outside” ?

4

because snow it’s not a cool temperature. Maybe it’s cool for people who live near of one of the poles. Are you russian?