A nNice wWeekend

The first letter of all nouns, verbs, adjectives, and adverbs is capitalized in the title.

Today was the best day I have ever've had in this summer week.

It was a cool day, great morechillier than I expected.

You could use "cooler" here, but this sounds better.

Yesterday, the weather forecast said that today iswould be the hottest day of the week, with the possibility of temperatures may up to 40 degrees.

But today, a heavy rainstorm came and it rained heavily all afternoon.

Therefore, I didn’t need to go to both my Math and myclass nor my extra English extra class.

I woke up early, did leisure activitiesrelaxed, and dìid homework.

After that, I had mucha lot of free time to do anything I wanted.

Because of the rain, I couldn’t go swimming, but; however, I was satisfied to experience the wind outside to cool my body, no need for the air conditioner tobe cooled by the wind from outdoors instead of using the AC, as it saves electricity.

If a day has such a high temperaturit's hot outside, I have to water those plants so that they won’t be dried ought and weaken.

On many sunny days, my body is always sweaty,When it's sunny outside, I sweat a lot; so, I usually have to take a bath more than twiceo times a day due to my bad smellbody odor.

But today, I just sat on the table and left the window open to feel the cool wind.

Those things nNo one can predict those things exactly, not even me.

Today was the best day I have ever had in this week of summer week.

It was a cool day, great morecooler than I expected.

Yesterday, the weather forecast said that today iswould be the hottest day of the week with temperatures mayreaching up to 40 degrees.

But today, a heavy rain came, and it rained all afternoon. / But today, it rained heavily all afternoon.

Therefore/So, I didn’t have/need to go to both my Math and myclass nor my extra English extra class.

"Nor" is used for negation or when the two choices are not happening

I woke up early, and did leisure activities and dì homework.

After that, I had mucha lot of free time to do anything I wanted.

Because of the rain, I couldn’t go swimming, but I was satisfied to(enough) experienceing the wind outside to cool my body, no need for the air conditioner towhich saved electricity. / I was happy enough saveing electricity by using the wind outside to cool my body instead of the air conditioner.

Furthermore, my plants on the balcony didn’t need to be watered / I didn't need to water my plants on the balcony.

Will I have more free time to relax and chillchill and relax?

Sounds more natural if you arrange the words in this order

Those things, no one can predict exactly,accurately predict, not even me.

Today was the best day I have ever had during this week of summer week.

It was a cool day, greateven more than I expected.

Yesterday, the weather forecast said that today iswould be the hottest day of the week with temperatures may up to 40 degrees.

But today, a heavy rain came and it rained all afternoon.

Therefore, I didn’t needhave to go to both myof my extra classes for Math and my English extra class.

I woke up early, did leisure activities and dìid homework.

After that, I had mucha lot of free time to do anything I wanted.

Because of the rain, I couldn’t go swimming, but I was satisfied to experience the wind outside to cool my body, and there was no need for the air conditioner to, which saved electricity.

If a day has such a high temperatures, I have to water those plants so that they won’t besuffer from drought and weaken.

But today, I just sat onat the table and left the window open to feel the cool wind.