532 



H. MOHN. METEOROLOGY. 



[NORW. POL. EXP. 



Hence we find the mean number of days in each month and in the 

 years, on which rain falls, and on which snow falls, and the mean number 

 of days with precipitation. 



PL IX (1 mm. = 1 day). 



Rain occurs only in the 6 months from May to October, and July has 

 the greatest number of rainy days. 



Snow occurs in every month, and May has the greatest number of snowy 

 days, November and December the least. 



The number of days with precipitation has an annual period, with a 

 minimum in November and December, and maxima in May, July and September. 

 The snowy days are of more than three times the frequency of the rainy days 

 in the whole year. The number of days in the year with precipitation being 

 180, every alternate day is, on an average, a day with snow or rain. 



The first and last days in the year with rain are 



