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Climatic Data OnLine (CDO)


Global Climate Station Summaries (TD3505)
ISD Summary - Present Weather (Frequency of Occurrence) Help

Purpose: This summary shows percent frequency of occurrence per hour of varying types of weather events (i.e. thunderstorms, precipitation, freezing or frozen precipitation, fog or haze) at one or more weather station locations. The summary will differentiate between months of the year and even time of day for all event types. Users define the weather station(s) by city and the period of time with which to base the frequencies of occurrence.


Date Restrictions

Choosing Date Range gives the user the available data over the period of record (e.g. between the selected dates).
Choosing Selected Dates gives the user the available data for the individual dates selected. Summaries will be generated over the entire range of years, days, and hours selected for each month.


Weather Event Abbreviations: Columns in the table are headed with abbreviations corresponding to the weather events defined below:

  • TSTM = Thunderstorm
  • RA/DZ = Rain, Rain Showers or Drizzle
  • FZRA/DZ = Freezing Rain or Freezing Drizzle
  • SN/IP = Snow, Snow Showers or Ice Pellets
  • FG = Fog
  • HZ/FU = Haze or Smoke
  • BLSN = Blowing or Drifting Snow
  • DU/SA = Blowing Dust or Blowing Sand
  • %Pcp = Percentage of weather observations with (any type of) liquid, freezing or frozen precipitation
  • %Obsc = Percentage of weather observations with one or more obstructions to visibility other than precipitation (i.e. fog, haze, smoke)
  • #Obs = The number of observations in the time range used to determine the percentage values for each weather event category

Time Information: Time ranges in the table are located in the leftmost column and are represented by a number for the hour from 0 to 23 as follows:

  • 0 indicates from midnight through 12:59 am UTC
  • 1 indicates from 1:00 am through 1:59 am UTC
  • 2 indicates from 2:00 am through 2:59 am UTC
  • 3 indicates from 3:00 am through 3:59 am UTC
  • 4 indicates from 4:00 am through 4:59 am UTC
  • 5 indicates from 5:00 am through 5:59 am UTC
  • 6 indicates from 6:00 am through 6:59 am UTC
  • 7 indicates from 7:00 am through 7:59 am UTC
  • 8 indicates from 8:00 am through 8:59 am UTC
  • 9 indicates from 9:00 am through 9:59 am UTC
  • 10 indicates from 10:00 am through 10:59 am UTC
  • 11 indicates from 11:00 am through 11:59 am UTC
  • 12 indicates from 12:00 pm through 12:59 pm UTC
  • 13 indicates from 1:00 pm through 1:59 pm UTC
  • 14 indicates from 2:00 pm through 2:59 pm UTC
  • 15 indicates from 3:00 pm through 3:59 pm UTC
  • 16 indicates from 4:00 pm through 4:59 pm UTC
  • 17 indicates from 5:00 pm through 5:59 pm UTC
  • 18 indicates from 6:00 pm through 6:59 pm UTC
  • 19 indicates from 7:00 pm through 7:59 pm UTC
  • 20 indicates from 8:00 pm through 8:59 pm UTC
  • 21 indicates from 9:00 pm through 9:59 pm UTC
  • 22 indicates from 10:00 pm through 10:59 pm UTC
  • 23 indicates from 11:00 pm through 11:59 pm UTC
  • ALL indicates from midnight to 11:59pm UTC

Please note that all times are UTC (Universal Time Coordinate) and must be adjusted for local time if desired.