- Day of the month ("calendar day").
Note that the time period is different between Standard Time and
Daylight Savings Time. The calendar day is midnight to midnight
Standard Time, but 1 a.m. to 1 a.m. DST.
- Maximum temperature. This is the highest temperature (°F)
recorded for the calendar day.
- Minimum temperature. This is the lowest temperature (°F)
recorded for the calendar day.
- Average temperature. The sum of the previous two columns,
divided by 2, and rounded, gives the value for this column.
- Departure from normal. This value is derived by
subtracting the "normal" temperature from the
"average" temperature (column 4). The "normal"
temperature is the 30-year smoothed average for the date, supplied by
the National Climatic Data Center.
- Heating Degree Days. The average temperature (column 4),
subtracted from 65, yields HDD. The amount of energy used for heating
is almost directly proportional to the number of heating degree days.
- Cooling Degree Days. Similar to (6a) above, CDD are
derived in the reverse manner. Sixty-five is subtracted from the
"average" temperature (column 4). Again, energy usage is the
main application of this value.
- Precipitation (Water Equivalent). This is the amount of
liquid precipitation, in inches, to the nearest hundredth, that has
fallen during the calendar day. If frozen or freezing precipitation
(snow, sleet, freezing rain, etc.) falls, it is melted and added to
the total of any liquid precipitation.
- Snowfall. This total, where measured, is the amount of
snow, hail, or ice pellets, in inches, to the nearest tenth, that
falls during the calendar day. In this case, the frozen precipitation
is not melted before measurement. Typically, snowfall is about
10 times its water equivalent (see column 7), but this ratio can vary
dramatically when snow falls at temperatures above freezing - or well
- Snow depth. The depth of frozen precipitation (whether
snow, ice, or hail) on the ground at 6 a.m. Standard Time (7 a.m.
DST), in whole inches, is shown here. The value is the actual depth of
the snow and ice, without including such things as grass underneath.
- Average wind speed. The calendar-day average wind speed
is shown here, in miles per hour, to the nearest tenth. This value is
normally derived by dividing the total "distance" of the
wind (as measured by an anemometer) and dividing by 24. Note that wind
speeds during the daylight hours tend to be substantially stronger
than those that occur at night.
- Fastest 2-minute speed. The strongest 2-minute average
wind speed that occurs during the calendar day is identified here. The
units are miles per hour. By definition, this value must be less than
the peak gust (column 18) and more than the daily average (column 10).
- Fastest 2-minute direction. (See column 11 for
information on the "fastest 2-minute wind.") This is the
prevailing direction of the strongest 2-minute wind, expressed in tens
of degrees. North is 36 (north could also be shown as 0, but 36 is
used here); east is 09; south is 18; west is 27; and all other
directions are in-between. Northeast, for example, would be shown as
either 04 or 05, since it is 45 degrees clockwise from north.
- Total minutes of sunshine. Where available, this value is
the approximate number of minutes that the sun is detected as shining,
according to a sunshine indicator.
- Percent of possible sunshine. Where available, this is
the ratio of the value in column 13 with the number of minutes between
sunrise and sunset, expressed as a percent.
- Sky cover. This entry is no longer available. It was
previously used to show the number of tenths of cloud cover, as an
hourly average through the daylight hours. This Not Available.
- Weather occurrences. The numbers presented in this column
are described in a chart at the lower right of the Form 6.
- Peak gust direction. This is the direction associated
with the strongest gust of wind measured during the calendar day. See
the description of column 12 for details on the coding.
- Peak gust speed. The strongest wind gust measured during
the calendar day is recorded here, in miles per hour.