Local climatological data. Indianapolis, Indiana. 1958

              jlncl'i a n xfo o //' 3 — th / f f c 1 y vr u s department of commerce weather bureau local climatological data with comparative data 1958 indianapolis indiana narrative climatological summary the climate of indianapolis briefly described is temperate with warm summers moderately cold winters and with precipi tation well distributed throughout the year the average annual temperature is 53 but has varied to as low as 49.6 1917 and as high as 56.4 1921 the lowest tem perature ever recorded at the airport was 19 below zero feb ruary 2 1951 but a reading of 25 below zero was recorded on january 5 1884 while the instruments were exposed in a small shelter outside a north window in a downtown area the pub lished highest airport temperature is 104 on july 14 1954 although a reading of 107 was obtained with roof top exposure on july 25 1934 one hundred four degrees was also recorded on several other occasions before the thermometers were moved to ground exposure . the average annual precipitation is 40 inches but varies from less than 30 to more than 55 inches in some years . heavy rains one inch or more in 24 hours occur about once a month light to moderate rains fall on about ten or twelve days each month annual snowfall averages 20 inches with considerable variation from year to year average cloudiness for the year is about 6/10 of complete coverage although about one hundred days are classed as clear , many of these days have up to 3/10 cloud cover days absolutely free of clouds are rare about one hundred and sixty-five days are classed as cloudy 8/10 or more cloud cover . heavy fogs occur about twenty days per year average wind velocity is 10 mph for the year ranging from 8 mph in july and august to 12 mph in march during about 50 of the time the wind is from the southwest quadrant s , sw,wd from each of the other directions it blows about 10 of the time tornadoes occasionally occur in the indianapolis area nine have been recorded only one caused extensive damage the growing season extends from april 23 to october 22 this being the average freeze-free period planting is general in may and crops generally mature before the first freeze in the fall freezing has occurred as late as may 11 the earliest fall freeze on record was on september 25th winters are moderately cold december averages 32 january is the coldest month with an average temperature of 29 and february has a definite upward trend with an average of 31 sudden changes occur frequently but severe cold is rare during an average winter a temperature of zero or lower is recorded on about four days in a severe winter this temper ature may be recorded ten or fifteen times and 10 below zero would be recorded about once occasionally there is a mild winter when zero is not reached at any time about three inches of precipitation falls during each of the winter months snowfall averages about five inches each winter month measurable snow 1/10 inch or more falls on about twenty two days during an average winter snow falls of three inches or more occur about two or three times during the winter . spring is a wet season with a sharp upward trend in tempera ture the average temperature gain is 1 for each three days or about 10 per month march and may are the wettest of the spring months with about four inches of precipitation about three and one-half inches fall in april temperatures average 40 in march 52 in april and 63 in may occasional warm spells occur in march with maximum temperatures sometimes as high as 80 90 is sometimes reached in may average snow fall during march is three or four inches but occasionally heavy snow falls in march--in fact the snowiest month on record was march 1906 when thirty inches fell some light snow falls in april but rarely in may summers ordinarily include periods of cool and pleasant hot and dry and very warm and humid weather occasionally hot dry continental winds from the west or southwest may prevail for several days the longest and most severe heat was in july 1936 when the temperature climbed to 100 or more for nine consecutive days sometimes in a summer very warm humid air from the gulf reaches the area and showers and humid muggy weather may persist for as long as two weeks more frequently the cool drier air masses from canada spread southeastward through the area and temporarily end such periods of uncom fortable weather before they have persisted for long tem peratures of 100 are rather rarely reached and not at all in some years ninety degrees or higher is recorded on only about 15 to 30 days each year june is the coolest of the summer months with an average of 72 . july average is 76 and august 74 . the normal rainfall of three or four inches during each of the summer months is adequate for production of good crops autumn is usually the most pleasant season except for occa sional rainy spells october is the driest of the fall months with less than three inches of rain september and november each have slightly more than three inches light snow occa sionally occurs in october and about an inch normally falls in november temperatures average 67 in september 56 in october and 42 in november hot weather is rather common during the early part of september on an average 90 is reached twice during september warm days are common in oc tober and november ordinarily has a few warm days indianapolis is mostly level or slightly rolling the only hill of consequence is crown hill elevation 840 feet from white river the terrain slopes gently upward to the east and west to an elevation of about 830 feet in irvington in the eastern part of the city the elevation at the weather sta tion which is located at weir cook airport seven miles south west of the central part of the city is 793 feet street level elevation at the former city office location was 718 feet msl prior to may 1 , 1885 , the thermometers were exposed in a small shelter outside a north window and it is impossible to tell how much they were affected by heat from the building from may 1 1885j to october 20 1937 all exposures were roof ex posures and should not be considered as representative of ground level conditions rainfall measurements were made at roof exposures prior to september 1 , 1939 , and from ground level thereafter data in this summary are based on records obtained from down town indianapolis prior to august 1 1931 and airport data thereafter city office data compared favorably with data observed at the airport except on clear calm nights when the temperatures at the airport were frequently as much as 5 to 10 lower than the temperature recorded downtown