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About the World Climate & Daylight Charts and Tables

Reading the Charts     The Tables     The Data     For Data Geeks     Global Warming     Links     Suggestions     Privacy

All of the World Charts and about 10% of the USA charts are based on data from the World Meteorological Organization. These are sometimes referred to as Series 1 in this site.

The rest of the USA charts are based on data from National Oceanic and Atmospheric Administration. These are sometimes referred to as Series 2 in this site. See About the USA Charts for more info about them.

Reading the Charts

Each chart makes it easy to see how climate for a particular location changes over the year, and how climate varies between locations.

All the charts use the same scales, for easy comparison between different locations. The scales fit the extremes of the data, although for a few stations (less than 1%) the values are truncated to fit the top of the chart section. The tables below the charts show the un-truncated values.

All of the climate values are monthly averages. For precipitation this means the average total monthly rainfall & snowfall.

Each chart is in three sections. Here we show each section (reduced in size), working from top to bottom, and explain what it contains.

Top section of climate chart

Top Section At the very top each chart is titled with the name of the location of the weather station where the data was gathered. Below the title you can find the latitude, longitude, elevation (where available) and the NOAA/WMO station id.

Next the months are listed, each given space proportional to the number of days it has, although that is hard to see.

The temperature section is next. High and low temperature is shown with red and blue lines, respectively. Average temperature (shown when highs and lows are not available) is green. A Centigrade scale is on the left, and a Fahrenheit scale is on the right.

Annual averages are shown by the color-coded triangles on the sides of the charts.

Middle section of climate chart

Middle Section Precipitation and humidity are shown in this section. Not all stations have all this data. As with temperature, high and low humidity is shown with red and blue lines, respectively, while average, if present, is brown. Precipitation is in green, snowfall in white.

Rainfall is displayed in millimeters on the left and tenths of an inch on the right.

Snowfall is measured in centimeters rather than millimeters, so to the use the same scales as for rain, what is displayed here is 1/10 of the actual snowfall measured. The actual values in centimeters and inches are shown in the tables.

Humidity is shown in percent, using the bottom half of the tenths of an inch scale on the right.

As for temperature, Annual averages are shown by the color-coded triangles on the sides of the charts.

Bottom section of climate chart

Bottom Section Daylight is shown by the yellow area, with a time-of-day scale on both sides. Time goes up on the scale, the the bottom edge of the yellow area represents sunrise, and the top edge represents sunset.

The amount of daylight is determined by the latitude of the location. However, the precise time of sunrise and sunset also depends on longitude and time zone. I don't have an automated way of matching longitudes to time zones, so the rise and set times are approximate. If the times were precise, the yellow daylight would be the same size and shape, but moved up or down in the chart a little bit. Also, daylight savings time would cause an offset while it was in effect.

The month labels are shown again, then the seasons are are labeled and shown with a tinted background that extends up the chart. Seasons for the southern hemisphere are reversed from the northern hemisphere - i.e., when it is winter in Europe it is summer in Australia.

The Tables

The tables show the climate data that the charts are based on. The background color for each data element matches the color the color used in the charts. For temperature and precipitation, the data is presented in both metric and 'English' units.

The Data

The data was originally gathered for the World Meteorological Organization (WMO), then processed by the National Climatic Data Center (NCDC), and finally provided by the National Oceanic and Atmospheric Administration (NOAA) via NOAA Global Climate Normals 1961-1990. These come from 4439 weather stations all over the world.

In most cases the data is 30-year averages, a standard climatological measurement period.

For Data Geeks

I make the charts with a series of hand-written software tools. I embed the NOAA data in PostScript language files, then use ImageMagick to create the .png images shown here.

Global Warming/Climate Change Predictions

thumbnail view of global warming map
Hadley Global Warming Map

(This section applies to both the World and USA pages)

The predicted temperature increases are from the Hadley Centre, a highly respected Climate Research Facility. We chose the output of the 'HadCM2' computer model from a variety of choices. This is considered a 'middle-of-the-road' projection. The 30-year target period is 2070-2100, compared to a baseline of 1960-1990.

See our links page for some selected sites that cover global warming.


Please let me know if you have any problems, questions, comments, or suggestions about the charts, this page, or anything else on the site.

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