Если на улице сильный ветер, одной прищепки мало.

In Russian, the verb to be is normally omitted in the present tense.

So:

• на улице сильный ветер literally looks like outside strong wind
• but it means there is a strong wind outside / it is very windy outside

This is completely normal Russian. In the past or future, a form of быть would appear if needed, but in the present it is usually left out.

Literally, yes, на улице means on the street. But in everyday Russian it very often means outside or outdoors.

In weather contexts, на улице is one of the most common ways to say outside:

• На улице холодно. = It’s cold outside.
• На улице дождь. = It’s raining outside / There’s rain outside.

So in this sentence, на улице is best understood as outside.

Because сильный has to agree with ветер.

• ветер is masculine
• singular
• nominative case

So the adjective also has to be:

• masculine
• singular
• nominative

That gives сильный ветер = strong wind.

If the noun changed, the adjective would change too:

• сильная буря = a strong storm
• сильное течение = a strong current

Because мало usually requires the genitive case.

So instead of nominative одна прищепка, you get genitive:

• одной прищепки

This is a very important pattern in Russian:

• мало воды = not enough water
• мало времени = not enough time
• одной прищепки мало = one clothespin is not enough

A helpful way to think about it is that Russian treats this structure a bit like there is too little of X. That is why the noun goes into the genitive.

Мало means too little, not enough, or insufficient.

In this sentence, it works as a predicate meaning is not enough:

• одной прищепки мало = one clothespin is not enough

This is a very common Russian pattern:

• Этого мало. = That’s not enough.
• Двух дней мало. = Two days are not enough.
• Одной прищепки мало. = One clothespin is not enough.

So although English uses a full phrase like is not enough, Russian often just uses мало.

Because прищепка is a feminine noun.

The word один changes like an adjective and must agree with the noun in gender, number, and case.

Since прищепка is:

• feminine
• singular
• genitive here

the form becomes:

• одной прищепки

Compare:

• один носок = one sock
• одна прищепка = one clothespin
• одной прищепки мало = one clothespin is not enough

Yes. The comma is required because Если на улице сильный ветер is a subordinate clause introduced by если.

Russian uses a comma to separate the if-clause from the main clause:

• Если на улице сильный ветер, одной прищепки мало.

If you reverse the order, you still need the comma:

• Одной прищепки мало, если на улице сильный ветер.

It can often have a general meaning in sentences like this.

So this sentence can be understood as:

• If there is a strong wind outside, one clothespin is not enough
• or more generally
• When it’s windy outside, one clothespin isn’t enough

In other words, it can describe a general rule or usual situation, not only one specific moment.

Yes, Russian word order is flexible, but not every version sounds equally natural.

These are both possible:

• Если на улице сильный ветер, одной прищепки мало.
• Одной прищепки мало, если на улице сильный ветер.

The first version is very natural because it presents the condition first and then the result.

Russian can move parts around for emphasis, but the original order is clear and standard.

Russian often uses the singular for weather phenomena where English might sometimes use either singular or plural.

So:

• сильный ветер = strong wind
• на улице сильный ветер = there is a strong wind outside

This sounds completely normal in Russian. Using the singular here is the expected choice.

It sounds like a practical general statement: a piece of everyday advice or common sense.

The structure is very natural for giving a rule of thumb:

• Если X, Y мало
• If X happens, Y is not enough

So the sentence feels like: if the weather is windy, using only one clothespin will not be sufficient.