Another climate element that makes Guilan prominent among other provinces is the relative humidity. Relative humidity is generally the highest in the early hours of the morning and the lowest in the middle of the day, as it is calculated based on the ability of the air to hold moisture at different temperatures. Colder air can potentially hold less moisture and warmer air is more likely to hold moisture. For example, even if the absolute humidity in the air does not change in the morning and at noon, because the temperature is low in the morning and at noon, the ratio of absolute humidity to low and high temperatures will vary at different times. Day and night, it increases its proportion in cold weather and reduces it in hot weather. However, although relative humidity is generally high in the morning, and low in the afternoon, it is still harder to tolerate midday in the warm seasons of the year because of the humidity. It is higher, so that the 30-year average of the two times of day and night, 6:30 and 9:30 pm, shows that the center of Gilan (Rasht) with 94 and 72% relative humidity, respectively The aforementioned hours are among the hottest cities in the provincial capitals. After Rasht, Ardabil has the highest humidity with 89% in early morning and Gorgan with 58% in Nimroz.


Humidity does not pose a problem for human comfort in conditions where the ambient temperature is not high, such as in the morning in Guilan, but high relative humidity if accompanied by high ambient temperature, It takes comfort from humans, and what climatologists call climate disruption. In fact, when the ambient temperature is high and relative humidity is high, body transpiration will not evaporate, or at least not evaporate properly. In other words, due to the high relative humidity, the evaporation does not evaporate to cool the body. In fact, the body’s immune system’s response to heat-induced transpiration is due to high air humidity, which prevents evaporation, resulting in the body’s ability to cool. This state of affairs, known as arid climatology, disrupts the human organism for routine, routine activity. The climate or climate of Gilan province among the provinces of the country has, in several respects, prominent features; Gilan’s climate is more rainy than anywhere else in Iran. For example, the city of Rasht, the geographical center of the province and the representative of the Gilan plain, is the most productive part of the country – with the exception of points in Gilan itself. The average annual rainfall of 30 years from 1345 to 1374 is estimated at 1401 mm. Among the provincial capitals of the country, except for Sari by the Caspian Sea, only Yasuj is located 831 mm after Rasht, which is somewhat close to it (National Statistical Yearbook: 2003). The other cities of the province namely Anzali, Astara and Lahijan had precipitation of 1554 mm (average rainfall of 53 years between 1330 to 2004) and 1379 mm (mean rainfall of years 1340 to 2004) (Guilan province statistical yearbook: 1383).


Precipitation is largely due to the presence of the Talesh and Alborz Mountains and is confined to the Gilan Plateau and its backbone, rising to about 1800 meters above sea level and then rapidly decreasing. However, it is not only altitude that reduces rainfall, but in some areas, the mountain wall also impedes moisture and reduces rainfall. For example, in Rudbar, which is 350 meters high, the annual rainfall amounts to only 370 mm, because of mountainous ridges and ridges that prevent sufficient moisture to reach the Sefidroud Valley in Rudbar, resulting in Imam Zadeh Hashem. Increasingly southward, the annual rainfall is gradually decreasing. In Manjil, just behind the West Alborz Mountains, the annual rainfall reaches 207 mm. Continuous and prolonged rainfall in Gilan generally begins in September. More than 5 percent of all annual rainfall falls in the four months of September, October, November and December. The beginning of the rain in September, when the rice harvest is not over yet, causes great damage to the rice harvest. So in recent years, farmers have begun cultivating some type of early rice so they can reap it before September arrives.