This is the 6098th most frequent Russian word.
среднесуточная
Average daily.
The word 'среднесуточная' here means 'average daily' and is used as an adjective to describe the 'temperature'.
Среднесуточная температура в этом месяце очень высокая.
The average daily temperature this month is very high.
Here 'среднесуточная' describes 'скорость ветра (wind speed)', indicating the average over a day.
Среднесуточная скорость ветра в этом регионе не превышает 15 км/ч.
The average daily wind speed in this region does not exceed 15 km/h.
In this sentence, 'среднесуточная' modifies 'влажность (humidity)', referring to the daily average.