Historical Weather

Historical weather provides temperature, precipitation, and degree day information for hundreds of locations across the United States back to January 1, 2008. You can view this information to get an idea of what the weather was like on a particular day or during a particular month. This information can be used to indicate which days it rained for construction and turf purposes or snowfall amounts for transportation purposes. The data can be viewed in daily, monthly or graphic formats.

Historical Weather Menu Option

Daily History

Historical weather data is available for locations across the United States. The historical data is taken from the nearest observation station for your location. Access this historical data by clicking the Historical Weather Menu option. The historical weather for your default location will appear in daily format. You can choose another location by either selecting one of your account locations from the drop down menu and click Go or by clicking the Map icon. If you select another city using the Map icon the drop down menu will change to a list of all available cities in the selected state. If you leave Historical Weather during the current login session and come back, you will be returned to the last city you viewed.

Two formats for selected locations are available: monthly and daily/hourly. Switch between the two formats by clicking the Daily History or Monthly History submenu option under the Historical Weather Menu option.

Historical Data

Actual Temperature
Hi	The high temperature recorded within a 24 hour period of midnight to midnight local time.
Lo	The lowest temperature recorded within a 24 hour period of midnight to midnight local time.
Normal Temperature
Hi	The average high temperature calculated using the most recent 30 year period, at the selected location on the selected date.
Lo	The average low temperature calculated using the most recent 30 year period, at the selected location on the selected date.
Departure Max	The difference between the actual high and the normal high.
Departure Min	The difference between the actual low and the normal low.
Precipitation
Liquid Amount	Total inches of liquid precipitation received within a 24 hour period of midnight to midnight local time. (Includes liquid equivalent of snow)
Snow Accum Est	Estimation of the total inches of precipitation received as snow within a 24 hour period of midnight to midnight local time.
Snow Cover Est	The total inches of snow cover estimated at midnight local time.
Degree Days
HDD (Heating degree day)	The difference between a reference value of 65°F (18°C) and the average outside temperature for that day. Designed to reflect the demand for energy needed to heat a home or business.
CDD (Cooling degree day)	The difference between a reference value of 65°F (18°C) and the average outside temperature for that day. Designed to reflect the demand for energy needed to cool a home or business.
Evapotranspiration
Evap	The sum of evaporation and plant transpiration from the earth's land surface to atmosphere measured daily.

Daily History

The default view is the daily data for the previous day. The data includes temperature, precipitation, degree days, and the 24-Hour NEXRAD precipitation estimate.

Change the day to view by clicking the calendar icon next to the date in Calendar. Select a different day from the calendar that appears and click Go. Data is available back to January 1, 2008.

Select the Hourly tab to view hourly data. The hourly data is viewed in a table format.

A note on hourly precipitation: not all National Weather Service (NWS) or Environment Canada (EC) observation stations report hourly precipitation. Some report every 3 hours, some every 6, and some not at all. A - (dash) in the precip column indicates there is no report available, while 0 (zero) indicates the station has reported and there was no precip detected that hour. Further, the stations may accumulate the precip in different ways. Because of these differences, the hourly totals don't necessarily add up to the same amount as reported in the daily value.

Symbol	Definition	Frequency
- (dash)	A dash located in the hourly total means no report is available.	Observation stations do not always use the same methods of data collection or report at the same frequency. Therefore adding up the hourly totals is not always equal to the total daily value.
0 or above	A numerical value of zero or above represents the total precipitation observed for that hour.

Due to the inconsistencies with the NWS and EC data, use the hourly precip to get a sense of timing, but use the daily precip value when you want a reliable precip quantity.

Monthly History

Click the Monthly History submenu option to view monthly data. The data for the current month up to the previous day will be listed. At the bottom the cumulative totals and average for the month are tracked. Data is available back to January 1, 2008.

Monthly Totals
Highest Temperature	The highest actual temperature recorded within the selected month at the selected location.
Lowest Temperature	The lowest actual temperature recorded within the selected month at the selected location.
Average Temperature	The average temperature calculated using all of the actual temperatures recorded within the selected month at the selected location.
Departure From Normal	The difference between the average temperature and the average of the normal temperatures during the selected month at the selected location.
Evapotranspiration	The sum of the daily evapotranspiration during the selected month at the selected location.
Heating Degree Days	The sum of heating degrees required during the selected month at the selected location to maintain an average temperature of 65°F (18°C) within a home or business.
Cooling Degree Days	The sum of cooling degrees required during the selected month at the selected location to maintain an average temperature of 65°F (18°C) within a home or business.
Total Precipitation	Total inches of liquid precipitation received within the selected month at the selected location. (Includes liquid equivalent of snow)
Total Snow Fall	Estimation of the total inches of precipitation received as snow within the selected month.
Normal Precipitation	The average amount of liquid precipitation calculated over the most recent 30 year period for the selected month at the selected location.

View a different month by selecting the month from the Month drop down menu and the year from the Year drop down menu and click Go. Data is available from the beginning of the prior year.

Historical RWIS

Historical RWIS data is available in the Pavement Forecast, Airport Operations and Alberta editions.

Historical observations from your RWIS sites can be viewed in either tabular or graphic format. If a value is highlighted with transparent red it has not passed the quality control checks. You may hover over the value for details. Level of service determines length of data availability.

Frequency of observations and available RWIS data will vary from one sensor to another.

Historical RWIS Data
Time	Time that data was observed, shown in local time.
Air Temp	Observed air temperature at the sensor location.
Dew Point	Observed dew point at the sensor location.
Precip Detection	Indicates whether or not precipitation is detected.
Barometric Pressure	Observed barometric pressure at the sensor location.
Wind Direction	Observed wind direction at the sensor location.
Visibility	Observed visibility, shown in miles, at the sensor location.
Wind Speed and Gust	Observed wind speed and gust at the sensor location.
Relative Humidity	Observed relative humidity at the sensor location.
Precip Accumulation	Rainfall amount or snowfall liquid equivalent from midnight GMT to present time.
Precipitation Rate	Amount of precipitation which was falling per hour, measured in inches or millimeters.
Precipitation Intensity	Observed intensity of precipitation at the sensor location.
Precipitation Type	The type of precipitation, if any, observed at the sensor location.
Last Precipitation	The date, start and end time of the last detected precipitation at the sensor location.
Surface Condition	Observed surface condition of road, runway or bridge at the sensor location.
Road, Runway or Bridge Temp	Observed temperature of road, runway or bridge surface at the sensor location.
Freeze Temp	Solution freeze point temperature.
Chemical Saturation	Percent of chemical saturation in the moisture.
Water Layer Depth	Current water depth on roadway surface.
Ice Percent	Percent of ice cover on roadway.
Surface Conductivity	Conductivity of the ice/liquid mixture on the pavement.
Chemical Percent	Percent of chemical saturation in the moisture.
Surface Salinity	Pavement salinity (salt content).
Sub Surface Temp	Observed temperature at a given distance below the ground surface.
Traffic Speed Min/Max	Highest/lowest vehicle speed as vehicles travel through traffic zone.
Avg Traffic Speed	Average vehicle speed as vehicles travel through traffic zone.

View a different date and/or location using the calendar and the location drop down menu. Click the Go button when selection is made.

Graphics

Historical weather can be viewed in graphic format by selecting the Graphics submenu under the Historical Weather Menu option. The graphics are national and do not have the option to select specific locations.

Historical Forecast

Historical Forecast data is an optional purchase and available only in the Pavement Forecast edition.

The historical forecast data is the actual 36 hour forecast produced for a RoadCast site within the last year. Data is available for a rolling year - meaning that on August 11, 2011, users will be able to view RoadCast forecast data from August 12, 2010 through August 11, 2011. The historical forecast can be saved to a file for further analysis. Only historical forecasts from RoadCast sites pertaining to your account are available. Thresholds and treatment recommendations are not archived with the forecast data and therefore may vary from the settings at the time the forecast was produced. Non RoadCast sites are not available.