62 SCIENTIFIC SURVEY OF NOTTINGHAM AND DISTRICT 



Mean Monthly Rainfall at Nottingham (Trent Lane, 82 ft. o.d.) 



IN Inches. 



Jan. Feb. Mar. Apr. May June Julj' Aug. Sep. Oct. Nov. Dec. Year 



Actual monthly mean 



1-74 1-45 1-59 1-34 1-80 1-85 2-28 2-40 1-5B 2-39 I'Sl 2-30 22-51 



Mean reduced to 30-day month 



1-68 1-55 1-54 1-34 1-74 1-85 2-20 2-32 1-56 2-31 1-81 2-23 22*51 



No. of rainy days* 



16 14 15 13 13 11 12 14 11 16 14 18 167 



*i.e. days on which 0*01 inch or more is recorded 

 Rainfall, as the above figures show, is distributed uniformly through the 

 year, there being a difference of but slightly more than one inch between 

 the mean for the driest month (April, 1.34 inches) and that for the 

 wettest month (August, 2.40 inches). Although October is commonly 

 the wettest month and autumn the wettest season in most parts of Britain, 

 a considerable quantity of rain is received during the summer months at 

 Nottingham. Thus July and August are distinctly wetter than any other 

 two consecutive months, and as much rain falls during the summer half- 

 year (April-September, 11.23 inches) as during the winter six months 

 (October-March, 11.28 inches). Indeed, for some stations, though by 

 no means all, August is definitely the wettest month, e.g. Nottingham 

 (Trent Lane), Beeston. At the Trent Lane station the three summer 

 months, June, July and August, account for 29 % of the total for the year, 

 a greater proportion than for any other three consecutive months although 

 the combined amount for October, November and December is but a 

 fraction less. 



The tendency towards a summer maximum was first demonstrated in 

 the case of Nottingham by E. J. Lowe as early as 1890 though it is now 

 widely recognised in other parts of eastern and east-central England. It 

 is explained by the occurrence of convection showers and also by rains 

 which accompany thunderstorms associated with local secondary de- 

 pressions. These develop frequently in the afternoon or early evening 

 during the summer months. 



The first four months of the year are all relatively dry and May brings 

 more rain to all parts of the county than any preceding month. Septem- 

 ber provides a notable respite in the sequence of somewhat rainy months 

 and incidentally allows time for surface drainage to proceed, otherwise, 

 owing to the configuration of the county, much land in the neighbourhood 

 of the Trent would readily become waterlogged, as indeed may happen 

 after prolonged rains at any time of the year. 



The average number of rainy days in the year at Nottingham is 167 

 and these too are distributed evenly through the months. Those with 

 fewest rainy days are June and September, whilst December has the 

 greatest number. It will be observed that, apart from October, the 

 months of maximimi rainfall are not those with the greatest nimiber of 

 rainy days, for the latter are related rather to the frequency of travelling 

 ' lows '. Thus December and January, being the months of maximum 

 cyclonic activity, have more rainy days than any other two consecutive 

 months. 



