Climate Graph Maker

How to Use the Climate Graph Maker

1. 1. Enter your data. One month per line: month, temperature, precipitation — Jan, 4.5, 55. The month name is optional and a first line of words names the columns. Columns copied from a spreadsheet work as they are; with decimal commas, separate cells with semicolons.
2. 2. Set the units. Say whether your numbers are in °C or °F and mm or inches, and choose the units to draw. The calculator converts for you — 25.4 mm to the inch.
3. 3. Choose the axis style. By default each axis is scaled to fit its data, with shared gridlines. In °C and mm, the Walter–Lieth option ties the axes at 10 °C to 20 mm.
4. 4. Label and export. Edit the title, pick a bar color, show the values if you want them, and turn on APA style figure for a paper. Download the SVG for sharp text at any size, or a PNG.

How a Climate Graph Is Built

A climate graph combines two kinds of data on one chart because they behave differently. Temperature is a continuous quantity, so its monthly means are joined by a line. Precipitation is a total for each month, so it is drawn as separate bars that rise from the baseline. Months run along the bottom from January to December, temperature has its own axis on the left, and precipitation has its own on the right.

This calculator gives both axes the same number of gridline intervals and puts their zero lines at the same height, so each horizontal rule means a round value on both sides. In a cold climate where some months are below freezing, the bars still start from the 0 °C line rather than from the bottom of the chart. The right axis is only labelled from zero upward, since there is no such thing as negative rainfall.

The Walter–Lieth Scale

A dual-axis chart can be misleading, because how the line sits against the bars depends entirely on the two scales. Heinrich Walter and Helmut Lieth's climate diagrams fix the relationship: the precipitation axis always runs at 20 mm for every 10 °C. With that ratio, a month where the temperature line is above the bars is arid (evaporation exceeds rainfall) and a month where the bars rise above the line is humid. Switch on the Walter–Lieth option when you need that reading. The original diagrams also compress precipitation above 100 mm; this tool keeps the same scale throughout instead and extends the axes to fit the data.

Reading the Annual Figures

Beneath the graph the calculator reports the figures a geography answer asks for: the mean annual temperature (the average of the twelve monthly means), the total annual precipitation (their sum), the annual temperature range (warmest month minus coldest month), and the warmest, coldest, wettest and driest months. They are calculated from the numbers you entered, converted to the units you chose.

• Describe the temperature first: the highest and lowest monthly values with their months, then the range.
• Then the precipitation: the total, the wettest and driest months and whether there is a wet season.
• Quote numbers with units — 18.6 °C, 68 mm — and say when the pattern is steady, seasonal or has a clear peak.
• Cite your data. National weather services publish climate normals; the WMO standard averaging period is 1991–2020. See how to cite a reproduced figure or table.

Frequently Asked Questions

How do you draw a climate graph?

Put the twelve months along the bottom. Mark a temperature scale on the left and a precipitation scale on the right, with zero at the same level. Plot mean monthly temperature as points joined by a line, and monthly rainfall as bars. Give the graph a title naming the place, and label both axes with units.

Why is temperature a line and rainfall a bar chart?

Temperature is a continuous quantity that changes smoothly from month to month, so a line shows the trend. Rainfall is a total accumulated over each month, so a separate bar shows each amount. Using different marks also keeps the two series from being confused.

What does 10 °C = 20 mm mean on a climate diagram?

It is the Walter–Lieth convention for the relative scale of the two axes: each 10 °C on the temperature axis lines up with 20 mm on the precipitation axis. Where the temperature line is above the precipitation bars the month is considered dry, and where it is below, humid.

How do you calculate mean annual temperature and annual range?

Add the twelve monthly mean temperatures and divide by twelve for the mean annual temperature. The annual range is the warmest month's mean temperature minus the coldest month's. Annual precipitation is the sum of the twelve monthly totals.

Can I make the graph in Fahrenheit and inches?

Yes. Tell the tool which units your data is in and which to draw: it converts °C to °F and mm to inches (25.4 mm per inch) before drawing. The Walter–Lieth scale is defined in °C and mm, so that option appears only when you draw in those units.

Where can I find climate data for a place?

National meteorological services publish monthly climate normals — for example NOAA in the United States, the Met Office in the United Kingdom and the Bureau of Meteorology in Australia. Use the monthly mean temperature and total precipitation for a recent 30-year period such as 1991–2020, and cite the source.