Weather lowdown. July is the warmest time of the year to visit Rome, Italy, when the city enjoys hot weather and plenty of sunshine. During this month, the average temperature starts off at around 25°C and gradually increases to 27°C toward the end of the month.If you visit in July you can expect to enjoy 14 hours of sunshine each day and only 23mm of rainfall spread across five days.With an average sea temperature of 25°C toward the coast, July is a great month to hit the beach during your holiday. .View at Tiber and St. Peter's cathedral in Rome, Italy.uring this month, the average temperature starts off at around 25°C and gradually increases to 27°C toward the end of the month. If you visit in July you can expect to enjoy 14 hours of sunshine each day and only 23mm of rainfall spread across five days.