The sSummer in Japan is more longer and very hot in recent years. Summer in Japan is longer and very hot in recent years.

The sSummer in Japan is morhas become longer and verya lot hotter in recent years. Summer in Japan has become longer and a lot hotter in recent years.

If you use "very" with comparative "-er" adjectives it sounds very unnatural, so I changed it to "a lot." You could also say "much hotter"; "a lot" is a little more casual.

The summer in Japan is morhas become longer and very hotter in recent years. The summer in Japan has become longer and hotter in recent years.

Originally, each day had a nameWe have names for the days based on how hot it wasthey are. We have names for the days based on how hot they are.

To me "each day had a name" sounds like every single day in the summer has a unique name "Originally" makes it sound like the names are no longer used/no longer exist. However, if you worded it like "Originally, we had three names for days based on how hot it was." it'd be okay, because then it sounds like the number of names has changed Honestly, not sure what a good way to translate 元々 is here. Possibly "We've always had names for..."

For example, a days with temperatures of 25°C or higher is "夏日(natsubi),", 30°C or higher is "真夏日(manatsubi)", ," and 35°C or higher is "猛夏日(mousyhobi)"." For example, a day with temperatures of 25°C or higher is "夏日(natsubi)," 30°C or higher is "真夏日(manatsubi)," and 35°C or higher is "猛夏日(moushobi)."

Spelling it like "natsubi," "manatsubi," and "moushobi" makes it easier to understand for English speakers.

For example, a days with temperatures of 25°C or higher is "夏日(natsubi)", 30°C or higher is "真夏日(manatsubi)", 35°C or higher is "猛夏日(mousyhobi)". For example, a day with temperatures of 25°C or higher is "夏日(natsubi)", 30°C or higher is "真夏日(manatsubi)", 35°C or higher is "猛夏日(moushobi)".

or if you want to use "days", change "is" to "are" to match the plural

For example, days with temperatures of 25°C or higher isare "夏日 (natsubi)", 30°C or higher is "真夏日 (manatsubi)", 35°C or higher is "猛夏日 (mousyobi)". For example, days with temperatures of 25°C or higher are "夏日 (natsubi)", 30°C or higher is "真夏日 (manatsubi)", 35°C or higher is "猛夏日 (mousyobi)".

There are different systems for writing Japanese pronunciation in English, so writing つ as "tu" might be correct in some systems, but it's more common to write it as "tsu", so I changed it.

However, There are already increasing days with temperatures of 35°C or higher in Japan are increasing. However, days with temperatures of 35°C or higher in Japan are increasing.

However, Tthere areis already an increasing number of days with temperatures of 35°C or higher in Japan. However, there is already an increasing number of days with temperatures of 35°C or higher in Japan.

However, There are already increasingnowadays there are more and more days with temperatures ofver 35°C higher in Japan. However, nowadays there are more and more days with temperatures over 35°C in Japan.

I changed "already" for "nowadays" as a translation of すでに, because I felt the meaning made more sense while still fitting the definition of すでに.

So days with temperatures of 40°C or higher is are neow named "酷暑日(kokusyhobi)"." So days with temperatures of 40°C or higher are now named "酷暑日(kokushobi)."

Again, "kokushobi" is easier to read than "kokusyobi."

So days with temperatures of 40°C or higher is are neow namcalled "酷暑日(kokusyhobi)". So days with temperatures of 40°C or higher are now called "酷暑日(kokushobi)".

You could say "newly named" but it sounds a little unnatural to me; I would just use "now"

So days with temperatures of 40°C or higher is have the new named of "酷暑日 (kokusyobi)". So days with temperatures of 40°C or higher have the new name of "酷暑日 (kokusyobi)".

The sSummer in Japan ihas high humidity so it's very humid and uncomfortable. Summer in Japan has high humidity so it's very humid and uncomfortable.

The sSummer in Japan is high humidity so it's very humidmuggy and uncomfortable. Summer in Japan is high humidity so it's very muggy and uncomfortable.

"muggy"="humid" Just to avoid repeating "humidity/humid" twice in the sentence

The sSummer in Japan ihas high humidity, so it's very humid and uncomfortable. Summer in Japan has high humidity, so it's very humid and uncomfortable.

I can't stand in at sunny spot because the sun light is too strong iwhen the tempaerature is higher than 40℃. I can't stand in a sunny spot because the sunlight is too strong when the temperature is higher than 40℃.

I can't stand atin sunny spots because the sun light is too strong iwhen the tempaerature is higher than 40℃. I can't stand in sunny spots because the sunlight is too strong when the temperature is higher than 40℃.

I can't stand at sunny spotin the sun, because the sun light is too strong iwhen the tempaerature is higher thanover 40℃. I can't stand in the sun, because the sunlight is too strong when the temperature is over 40℃.

"Sunny spot" isn't unnatural, but when talking about this kind of thing (the intensity/heat of sunlight), people usually just say "the sun". For example, "make sure to stay out of the sun between 11am and 4pm".

I don't like hoeat in summer, but I can only try to endure it. I don't like heat in summer, but I can only try to endure it.

"Trying to" endure it sounds more natural.

I don't like hothe heat in summer, but all I can onlydo is endure it. I don't like the heat in summer, but all I can do is endure it.

I don't like hothe heat in summer, but I can only endure. I don't like the heat in summer, but I can only endure.