How can I read a climate graph with monthly temperature and precipitation?
Quick answer
Read the month labels first, then match each variable to its labeled axis and units. Many climate graphs use bars for precipitation and a line for temperature, with separate scales on opposite sides, but layouts can vary. Follow each bar or line to its own scale—not the other variable’s scale—then compare months to find higher and lower values and describe the pattern.
The question, the details, the next step.
I’m looking at a climate graph with bars and a line. What should I check before explaining it, and how do I avoid mixing up the scales?
Start with the labels rather than assuming what the shapes mean. Find the months along the bottom, identify the variable named beside each vertical axis, and note the units and scale marks. A climate graph shows average temperature and precipitation through the year. One common layout uses precipitation bars with its scale on the left and a temperature line with its scale on the right, but layouts can vary. Check the particular graph before interpreting it. [S1]
Trace each symbol to its own scale: read a bar against the axis for its variable and a line point against the axis for its variable. For example, suppose an illustrative graph labels precipitation in millimetres from 0 to 100 on the left and temperature in degrees Celsius from −10 to 30 on the right. A bar reaching 60 reads as 60 millimetres on the left scale. A line point at the same visual height does not automatically mean 60 degrees; use the right scale. These are made-up values, not climate observations.
A useful note is: “The bottom axis shows months; the left axis measures [variable and units]; the right axis measures [variable and units]. The bars represent [variable], and the line represents [variable].” Fill in the blanks from the graph.
Once I know the axes, what questions can help me describe the monthly pattern clearly?
Read one variable at a time, then compare the patterns. Ask: Which month has the highest temperature point, and which has the lowest? Which month has the tallest precipitation bar, and which has the shortest? Do values rise, fall, or stay fairly similar across neighboring months? NOAA’s graph-reading examples use monthly values to identify average summer temperatures and the months with the most or least rain. [S2]
Try this template: “The temperature line is highest in [month] and lowest in [month]. The precipitation bars are tallest in [month] and shortest in [month]. From [month] to [month], temperature [rises/falls/stays similar], while precipitation [rises/falls/stays similar].” Use the graph’s labels to fill in the months and units. If neighboring points or bars look close, describe them as similar rather than claiming a large change.
Can you show a short annotated example, and what should I say if I don’t know what period the averages cover?
Here is an invented mini-example for practice, not a report for a real location. Assume the horizontal axis lists Jan, Feb, and Mar; the left axis is precipitation in millimetres; the right axis is temperature in °C; bars show precipitation and the line shows temperature:
Month: Jan Feb Mar
Rain bar: 20 50 30 mm
Temp line: 5 8 12 °CAnnotation: “The precipitation bar is tallest in Feb (50 mm) and shortest in Jan (20 mm). The temperature line rises from 5°C in Jan to 12°C in Mar.” These conclusions follow the assumed labels and sample values. Check the actual graph’s units and scales before using this style of description.
If the graph does not state the averaging period, don’t guess it. You can describe what the graph displays, but check its caption or source before calling the values averages for a particular set of years. NOAA’s cited example concerns U.S. climate normals averaged over 1991–2020; its page is archived, so it supports graph-reading concepts, not a current data lookup. [S2]
A practical checklist
Read the month labels and both vertical-axis labels.
Record the units and scale marks for each variable.
Confirm which symbol represents each variable; do not assume the layout.
Read bars and line points against their own labeled scales.
Identify the highest and lowest months for each variable.
Describe rises, falls, or similar values, and check the caption for the averaging period.
A few more useful answers
Does the tallest bar always mean the warmest month?
No. First check what the bars represent. In the common layout described here, bars show precipitation and the line shows temperature; read each using its labeled axis. [S1]
Can I compare the apparent height of a bar with the height of the temperature line?
Not as a direct comparison of numerical values when the graph uses separate scales. Read each mark against the axis and units assigned to that variable. [S1]
What if the graph has no units or clear labels?
Avoid assigning values or units based on appearance. Look for a caption or accompanying explanation; if the labels remain unclear, describe only what is visibly shown and note the limitation.
Sources
References used for this guide.
- [S1] NOAA Global Monitoring Laboratory: What Is Climate? gml.noaa.gov · Checked
- [S2] NOAA Climate.gov: 1991–2020 Climate Normals Climographs prod-01-asg-www-climate.woc.noaa.gov · Checked