הלוואי שהתחזית תטעה ולא תהיה לחות כזאת גם מחר.

הלוואי means if only, I wish, or sometimes I hope, but it usually sounds stronger and more emotional than plain אני מקווה.

So הלוואי... often introduces a real wish, especially when the speaker really wants something to happen or not happen.

The ש־ means that.

So הלוואי ש... is literally like saying I wish that....

In this sentence:

הלוואי שהתחזית תטעה...
= I wish that the forecast is wrong...

This is a very common structure in Hebrew.

Because the speaker is talking about a wish concerning the future or an unknown result.

תטעה is the future form of טעה: to be mistaken / to be wrong / to make a mistake.

So here שהתחזית תטעה means that the speaker wishes the forecast will turn out to be wrong.

After הלוואי, Hebrew very often uses the future tense for wishes about the present or future.

Because התחזית is a feminine singular noun.

Hebrew verbs have to agree with their subject in gender and number, so:

• התחזית תטעה
• not התחזית יטעה

A native English speaker often notices this because English verbs do not change for gender, but Hebrew verbs do.

Yes, it works very naturally.

The verb טעה can be used for people, but also for things like clocks, calculations, assumptions, and forecasts.

Examples:

• המורה טעה = the teacher was wrong
• השעון טועה = the clock is wrong
• התחזית טעתה = the forecast was wrong

So התחזית תטעה is a natural way to say that the forecast will be wrong.

Hebrew often omits the second ש־ when two clauses are connected.

So the sentence says:

הלוואי שהתחזית תטעה ולא תהיה לחות כזאת גם מחר

But you could also say:

הלוואי שהתחזית תטעה ושלא תהיה לחות כזאת גם מחר

Both are natural. The version without the second ש־ is a little more streamlined.

Here תהיה is part of an existence pattern: there will be.

So:

• תהיה לחות = there will be humidity
• לא תהיה לחות = there will not be humidity

This is very natural Hebrew. English often uses there will be, while Hebrew uses forms of היה.

So ולא תהיה לחות כזאת means and there won’t be humidity like this.

Because לחות is feminine singular.

Hebrew often makes the future verb agree with the noun that follows in this kind of sentence:

• תהיה בעיה = there will be a problem
• תהיה לחות = there will be humidity
• יהיה זמן = there will be time

So since לחות is feminine, the sentence uses תהיה.

Literally, it means such humidity.

In more natural English, that is usually:

• humidity like this
• this much humidity
• this kind of humidity

So the speaker is not just talking about humidity in general, but about this unpleasant level or type of humidity.

Because כזאת has to agree with לחות, and לחות is feminine singular.

So:

• masculine singular: כזה
• feminine singular: כזאת

Compare:

• מזג אוויר כזה = weather like this
• לחות כזאת = humidity like this

גם מחר means tomorrow too or also tomorrow.

The idea is that the humidity is already bad now, and the speaker hopes it will not continue into tomorrow as well.

So the sentence implies something like:

I hope the forecast is wrong and it won’t be this humid tomorrow too.

Yes, גם מחר is the natural order here.

Hebrew often places גם directly before the word or phrase it modifies. Here it modifies מחר, so:

• גם מחר = also tomorrow

That is the most straightforward and natural phrasing in this sentence.

A common pronunciation would be:

halvay shehatakhazit tit'eh velo tihye laḥut kazot gam maḥar

A few useful pronunciation notes:

• הלוואי = halvay
• התחזית = hatakhazit
• תטעה = tit'eh
• תהיה = tihye
• לחות = laḥut
• מחר = maḥar

The letters ח in לחות and מחר are the throaty sound that English does not really have.