Weather Station Data (TMY) Tool User Guide
Weather Station Data (TMY)
Red Calc Tool User Guide
What this tool can do for you
First, the embedded Google map feature helps you find the closest
(TMY) weather station when your location is close to a state/province or
national border and the closest station is actually in a different
state/province/country. These are the same weather stations that are
used in the ASHRAE 62.2-2013 tool, for example.
Second, the tool's interactive table and chart help you explore the
the Typical Meteorological Year (TMY) data for each of 1,100 weather
stations in North America. This hourly data is the foundation for
most building energy simulation software. (See the "Typical
Meteorological Year data" section below.)
Weather station map displayed
Weather data chart displayed
Latitude for selected location.
Longitude for selected location.
Altitude (elevation) for selected location.
For the date range selected, a table including low, average,
and high values for dry bulb
temperature, dew point temperature, and wind speed.
For the date range selected, a chart showing daily averaged dry bulb
temperature, dew point temperature,
and wind speed.
Clicking the label for any input or result will cause a
popup help box to appear. This help box includes the
allowed and normal values (for inputs).
This tool requires a reasonably fast internet connection to perform
well, as compared to other RED Calc tools that came before it. A
slow internet connection will be most noticeable when using the
Google map. You may prefer to uncheck the "Show map" check box to
disable the map feature. (It is not required in order to use the rest of
the tool.) Also, each time you choose a different weather station,
the weather data for that station must be downloaded, causing a
noticeable delay with a slow internet connection. The only
recourse in this case is to seek out a faster connection.
Check "Show map" to show the Google map with the weather stations. The
weather stations are displayed as pink dots. The selected weather station
is centered in the map viewing area and is displaced as a red dot. Otherwise,
the map functions like a typical Google map.
The drop-down selectors for selecting the weather station are interconnected
with the map; change one or more of the drop-down selections and the map changes. Change
the map weather station selection, and the drop-downs change.
The date range above the table allows you to select the month and day for the
beginning and end dates of the displayed table and chart data. Because the tool uses
Typical Meteorological Year data, there is no year selection.
Check "Show chart" to display the interactive chart. Refer to Interactive Chart
Use below for more information.
The low (high) values in the table will most likely be lower (higher)
than the lows (highs) in the chart. This is because the chart
plots daily average values.
For an explanation of the derivation of the TMY3 (US) and CWEC (Canadian) weather
data used for this tool, please see the Related external resources below.
This tool includes a powerful interactive chart that can be used to display
the results; it may also be used for educational, sales,
and marketing purposes. For example, you can save a chart in one of four different
file formats, embed it into your customer reports, or print it separately.
Tips for using the interactive chart:
You may zoom in on the chart weather data by dragging an area
on the chart with your mouse or by zooming (stretching or
pinching) with two fingers on your touch device. [On a touch device,
you may swipe the date range forward (left) or back (right) with one finger.]
Reset by clicking/touching the "Reset zoom" button.
Click/touch the labels "Dry bulb", "Dew point", and "Wind speed" in the
legend below the chart to turn the corresponding data lines on or off.
Click/touch the menu icon in the upper right corner of the chart
to show the choices for printing the chart or downloading it as an
image file in PNG, JPEG, PDF, or SVG format. You are free to use the
downloaded image in any way, including reports,
presentations, websites, as long as the attribution for
"Residential Energy Dynamics, LLC" is included.
If you save the chart as an SVG file, you can change the
title or any other chart element with the use of third-party
software. Examples of third-party software include Inkscape
(a free version is available) and Adobe Illustrator.
Typical Meteorological Year weather data
The weather station data used for this tool - Typical Meteorological
Year (TMY) data - comes from two sets of data: TMY3 with 1020 US locations,
and CWEC with 80 Canadian locations. Both of these sets of weather
data include many types of hourly weather measurements. For this tool,
we have chosen to focus on the three
most commonly used. (See the "Related external resources" section below.)
The typical meteorological year data for a location is comprised of twelve separate
typical months of data spliced together to form an entire year.
Each typical month of data is the actual data for that month at that
location, for some year in the past 15 years (or so). It was chosen
because it was the most "typical" in the sense that its average
temperature, humidity, wind speed, etc. was closest to the 15 year
averages for that month. So it is entirely possible that the typical
meteorological year at a location includes January data from 2002,
February data from 1999, etc. Each month is chosen
independently of the others.
TMY data is often used for building energy simulation to assess
heating/cooling loads and for solar analysis to evaluate photovoltaic,
hot water, and other solar projects.
The map below shows the TMY3 weather station locations for the United States.
Source: National Renewable Energy Laboratory (NREL)
Select the weather station closest to the site you are analyzing. If your
location is close to a state border, you might find the closest weather
station is in another state. The map feature is helpful for determining
We recommend you NOT use the uncertainty feature for this tool
because the tool is merely reporting weather data for the Typical Meteorological
Year. If the uncertainty reporting is on, go to the "Preferences" RED
Calc Free tool to set the "Uncertainty feature" to off.
ASHRAE 62.2-2013 Ventilation:
Determine whole-building ventilation requirements for new and existing
dwellings, with the choice of using advanced blower door options and
the alternative compliance path. It requires the selection of the
closest (TMY) weather station.
Related external resources