Learn Hardcore Russian: Я кладу плед на плечо, потому что на улице холодно. - I put a blanket on my shoulder because it is cold outside.

The imperfective present tense describes an action in progress or a general action:
Я кладу плед… = I’m putting the blanket… / I put the blanket (now).
The perfective verb has no true present tense; its “present” forms have future meaning:
Я положу плед… = I will put the blanket…

So you cannot say “I am putting” with положить; you must use класть → кладу.

Can I say ложу instead of кладу?

No. Native speakers consider ложу (from a supposed ложить) incorrect in standard Russian.

To say “I put/lay (something)”:

Use класть → кладу for the present/imperfective:
Я кладу плед на плечо.
Use положить → положу for the future/perfective:
Я положу плед на плечо. (I will put the blanket on my shoulder.)

There is no standard verb ложить in modern literary Russian; avoid it.

Why is it плед and not одеяло? What is the difference?

Both refer to something like a blanket, but there is a nuance:

плед – usually a throw blanket, smaller, often plaid, used on a sofa, chair, or shoulders.
одеяло – a bed blanket/duvet, what you sleep under at night.

Since the context is putting it on your shoulder because it’s cold outside, плед (a throw) is more natural than одеяло (a big bed blanket).

Why is it на плечо and not на плече?

The preposition на can take either accusative (direction) or prepositional (location):

На + accusative = onto (movement to a surface):
кладу плед на плечо – I put the blanket onto (my) shoulder.
На + prepositional = on (location, no movement):
Плед лежит на плече – The blanket is lying on (my) shoulder.

Because the verb кладу expresses movement/placing, Russian uses на + accusative → на плечо.

Why is плечо singular here? Would на плечи also be possible?

Плечо = shoulder (singular), плечи = shoulders (plural).

на плечо – onto one shoulder (or just stylistically singular).
на плечи – onto (both) shoulders.

Both can be grammatically correct, but they describe slightly different images:

Я кладу плед на плечо – suggests putting it over one shoulder (or more vaguely over the shoulder area).
Я кладу плед на плечи – suggests draping it over both shoulders.

The sentence chooses singular, so you imagine one shoulder or just a general “over the shoulder” gesture.

Why is there no мой / своё before плечо? Why not на моё плечо?

In Russian, with body parts and clothes, the possessive pronoun (мой, твой, свой etc.) is often omitted when it’s obvious the body belongs to the subject:

Я кладу плед на плечо.
Literally: I put the blanket on (the) shoulder → understood as on *my shoulder*.
Он поднял руку. – He raised (his) hand.

You usually add the possessive only if:

You want to emphasize whose body it is (someone else’s):
Я кладу плед на его плечо. – onto his shoulder.
There could be ambiguity.

So на плечо here naturally means onto my shoulder.

What case is плед, and what case is плечо in this sentence?

плед – accusative singular (direct object of кладу).
For inanimate masculine nouns, accusative = nominative, so the form doesn’t change:
плед (nom.) → плед (acc.).
плечо – accusative singular after на with motion (onto):
Nominative: плечо → Accusative: плечо (same form; neuter).

So both words are in the accusative, but for different reasons:
плед as direct object, плечо as the destination of movement after на.

Could I say Плед лежит на плече, and what would be the difference?

Yes, and it would mean something slightly different:

Я кладу плед на плечо… – I am putting the blanket onto my shoulder… (focus on the action of placing).
Плед лежит на плече… – The blanket is lying on my shoulder… (focus on the result / state).

First sentence: dynamic, uses класть + на (acc.).
Second sentence: static, uses лежать + на (prep.).

Why is there a comma before потому что?

Потому что introduces a subordinate clause of reason (because), so Russian punctuation normally requires a comma before it:

Я кладу плед на плечо, потому что на улице холодно.

Structure:

Main clause: Я кладу плед на плечо
Subordinate clause (reason): потому что на улице холодно

Russian almost always separates the main and subordinate clauses with a comma in this pattern.

Is потому что always the same as English “because”? Are there any special things to know?

In most everyday cases, потому что = because.

Some useful notes:

It introduces a full clause:
- …потому что на улице холодно. – because it is cold outside.
Word order can be reversed:
Потому что на улице холодно, я кладу плед на плечо. – This sounds a bit more formal or explanatory, but is correct.
Don’t confuse with потому, что (with a comma inside), which is a rarer, more formal construction with a slightly different meaning/structure. For learners, treat потому что (no internal comma) as “because.”

Other “because”-like words:

так как – rather formal, often at the beginning of the sentence.
ведь – more like “you know, after all,” not a direct equivalent of because.

Why is the phrase на улице холодно used instead of something like есть холодно?

In Russian, weather and general conditions are typically expressed with a predicative adverb/adjective like холодно, жарко, тепло, сыро, etc., without a verb like “to be” in the present tense:

На улице холодно. – It’s cold outside.
Здесь жарко. – It’s hot here.

Key points:

There is no “it is” equivalent in the present tense; Russian simply says холодно.
You cannot say есть холодно for “it is cold.” The verb есть as “to be” is normally omitted in the present tense in such sentences.
На улице literally means “in the street” but idiomatically also “outside, outdoors.” So на улице холодно naturally means “it’s cold outside.”

Can I change the word order to Потому что на улице холодно, я кладу плед на плечо or Я кладу на плечо плед?

Yes, both are grammatically possible, with slight stylistic/intonation differences:

Потому что на улице холодно, я кладу плед на плечо.
- Puts the reason first.
- Feels a bit more formal, explanatory, or like an answer to “Why are you doing that?”
Я кладу на плечо плед.
- Emphasizes плед a bit more (end-focus).
- Still correct, but the neutral, most typical order is
  Я кладу плед на плечо.

Russian word order is flexible; you generally put the new or emphasized information closer to the end.

Could I drop Я and just say Кладу плед на плечо, потому что на улице холодно?

Yes, in colloquial speech it’s possible:

Кладу плед на плечо, потому что на улице холодно.

Russian allows dropping the subject pronoun when the verb ending clearly shows the person (кладу = 1st person singular, “I”).

However:

Including Я is more neutral and clear, especially in written or careful speech.
Dropping Я can sound slightly more informal or like a continuation of a previous context where it’s obvious who is speaking.

So both versions are possible; the original with Я is the most standard.