“Tam frigidus imber non saepe cadit,” inquit avia, “sed cum hiems aspera sit, tamen hilaritas bona nos iuvat.”

Frigidus is masculine because it agrees with imber, which is a masculine noun meaning rain.

In Latin, adjectives must match the noun they describe in:

• gender
• number
• case

So here:

• imber = masculine, singular, nominative
• frigidus = masculine, singular, nominative

A common beginner mistake is to assume the meaning decides the gender, or that all weather words are neuter or feminine. But grammatical gender in Latin is something you simply learn with each noun. Imber happens to be masculine.

Here tam means so or so very:

• tam frigidus imber = such cold rain / rain so cold

You are right that tam is often paired with quam:

• tam... quam... = as... as...

But tam can also stand by itself just to intensify an adjective:

• tam frigidus = so cold
• tam bonus = so good

So nothing is missing. Latin often uses tam on its own.

The two are similar, but not exactly the same.

• non saepe cadit = it does not fall often
• saepe non cadit = it often does not fall

The first denies the frequency.
The second suggests repeated occasions on which it does not happen.

In this sentence, non saepe cadit is the natural way to say that such cold rain is infrequent.

Inquit avia means said grandmother or grandmother said.

Latin often places a speech verb like inquit inside or after direct speech, not just before it. So instead of putting avia inquit at the beginning, Latin can interrupt the quotation:

• ..., inquit avia, ...

This is very normal literary Latin.

A couple of useful points:

• inquit is a common verb used especially with direct quotations.
• avia is nominative singular, the subject: grandmother.

So the structure is:

• first part of the quotation
• inquit avia
• second part of the quotation

Because cum here introduces a clause that uses the subjunctive, and sit is the present subjunctive of esse.

In this sentence, cum is best understood as although:

• cum hiems aspera sit = although winter is harsh

This is called a concessive cum-clause, and concessive cum normally takes the subjunctive.

So:

• est = indicative, simple statement
• sit = subjunctive, used here after concessive cum

The word tamen later in the sentence strongly supports this reading:

• cum ... sit, tamen ...
• although ... , nevertheless ...

Here it most likely means although.

Latin cum can have several meanings depending on context:

• when
• since
• although

The clue here is tamen in the main clause:

• cum hiems aspera sit, tamen hilaritas bona nos iuvat

That pattern strongly suggests a concessive idea:

• although winter is harsh, nevertheless good cheer helps us

So although cum can mean several things, in this sentence although is the best choice.

They are doing slightly different jobs.

• sed = but
• tamen = nevertheless / still

Here is how the sentence works:

1. Tam frigidus imber non saepe cadit
   Such cold rain does not fall often

2. sed introduces the next idea in contrast:
   but

3. cum hiems aspera sit adds a concessive clause:
   although winter is harsh

4. tamen marks the main clause after that concession:
   nevertheless good cheer helps us

So sed connects the two bigger statements, while tamen answers the concessive cum clause. Latin often likes this neat pairing.

Yes, bona hilaritas would also be possible.

Latin adjective position is more flexible than English word order. Both of these can mean good cheer:

• hilaritas bona
• bona hilaritas

In this sentence:

• hilaritas = nominative singular feminine
• bona = nominative singular feminine, agreeing with hilaritas

The adjective after the noun is completely normal Latin. Sometimes word order gives slight emphasis or rhythm, but here the main point is simply agreement.

Because iuvare normally takes a direct object in the accusative.

So:

• nos iuvat = it helps us
• nos is accusative plural

This is different from some English expressions where we might think in terms of to us. In Latin, iuvat usually works more like helps or delights, with a direct object:

• me iuvat = it helps me / it pleases me
• nos iuvat = it helps us

So nobis would not be the normal choice here.

The main verbs are in the present tense:

• cadit = falls
• sit = may be / is in the subjunctive
• iuvat = helps

The present tense here expresses a general truth or a general situation, not just a one-time event. The grandmother is making a broad statement:

• such cold rain does not often fall
• winter may be harsh
• good cheer helps us

Latin often uses the present tense in this way, just as English does:

• Winter is cold
• Rain falls
• Hope helps us

Yes, the word order is flexible, and Latin often arranges words for emphasis, balance, or style rather than following a fixed English-like order.

For example:

• Tam frigidus imber non saepe cadit puts emphasis early on tam frigidus imber — such cold rain

And:

• tamen hilaritas bona nos iuvat places tamen prominently near the front, marking the contrast clearly.

Because Latin uses endings to show grammatical roles, many rearrangements are possible without changing the basic meaning. But the original order sounds natural and expressive.

So the sentence is not “backwards”; it is just following normal Latin habits of emphasis and style.