Interpret climate graphs and data tables by reading values, calculating ranges and totals, and describing patterns and trends

What this dot point is asking

This skill asks you to read a climate graph and a data table accurately, to do simple calculations such as the temperature range and total annual rainfall, and to describe the patterns you see in clear geographical language. Climate graphs appear often in the data-response section, so you need to be quick and exact. The central idea is that a climate graph packs a place's whole year of weather into one picture, and your job is to read it off and explain what it shows.

The answer

Reading a climate graph

A climate graph combines two things in one diagram. Rainfall is shown as bars, read against the axis on one side (usually the right) in millimetres. Temperature is shown as a line of points, read against the axis on the other side (usually the left) in degrees Celsius. The months January to December run along the bottom. To read a value, find the month, go up to the top of the bar or to the line point, then across to the correct axis, and write the figure with its unit.

Calculating the temperature range

The temperature range is how much the temperature varies across the year. Work it out as:

A small range (only a few degrees) suggests an equatorial climate near the Equator; a large range suggests a place far from the Equator or deep inside a continent.

Calculating total annual rainfall

The total annual rainfall is the sum of all twelve monthly figures added together. Always include every month, even the dry ones. A large total with rain in every month points to an equatorial climate; a large total concentrated in a few months points to a monsoon climate; a small total points to a dry climate.

Describing patterns and trends

When asked to describe, do not just list numbers. Use a clear structure: state the overall pattern first, then give figures to support it, then note any anomaly (a month that breaks the pattern). For rainfall, identify the wettest and driest months and whether there is a clear wet and dry season. For temperature, say whether it is high or low, and whether it stays steady or varies. Words like "rises," "falls," "peaks," "stays constant" and "ranges from ... to ..." score well.

Examples in context

Example 1. Reading Singapore's climate graph. A climate graph for Singapore shows temperature staying near 27 degrees Celsius all year (a range of only about 2 degrees) and rainfall high in every month with a wetter spell late in the year during the Northeast Monsoon. Reading it off gives a textbook equatorial pattern: hot, constant and wet throughout.

Example 2. Comparing two stations in a data-response. A question might give a table for an equatorial station and a monsoon station. By adding the columns and finding the ranges, a student can show the equatorial station has rain every month and a tiny range, while the monsoon station has a clear dry season and a slightly larger range, using figures to justify which is which.

Try this

Q1. A climate graph shows a highest monthly temperature of 31 degrees Celsius and a lowest of 19 degrees Celsius. Work out the temperature range. [1 mark]

• Cue. Highest minus lowest: $31 - 19 = 12$ degrees Celsius.

Q2. State two things you should always include when describing a rainfall pattern from a climate graph. [2 marks]

• Cue. An overall statement (for example wet all year, or a clear wet and dry season) and supporting figures with units, naming the wettest and driest months.

Q3. A station has rainfall above 200 mm in every month and a temperature range of just 2 degrees Celsius. State which climate type this suggests and give one reason. [2 marks]

• Cue. Equatorial; heavy rain in every month with no dry season and a very small temperature range are typical of places near the Equator.