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Quiz yourself on Graph, Chart and Data SkillsGet your flashcardsBuild my revision planTrack my progress🌡️ Reading Climate Graphs in Detail
Climate graphs (also called climographs) appear in almost every geography exam — you need to be able to read them quickly and accurately. The structure is always the same: temperature shown as a line graph, precipitation shown as a bar chart, both on the same diagram with months along the x-axis. There are always two y-axes — check which scale is for temperature and which is for precipitation before you start reading values.
Step-by-Step Reading Method
Read the peak and trough of the temperature line. Note the month and the value in °C. Example: "The hottest month is July at 24°C; the coldest is January at 3°C."
Subtract the coldest month temperature from the hottest: Annual range = highest – lowest. Example: 24°C – 3°C = 21°C annual temperature range. A large range (over 20°C) indicates a continental interior climate. A small range (under 10°C) indicates an oceanic or tropical climate.
Read the tallest and shortest bars. Note month and value in mm. Example: "The wettest month is August at 85 mm; the driest is February at 25 mm."
Add up the 12 monthly bars, or estimate by averaging and multiplying. This does not need to be exact — an estimate with a clear method scores marks. Example: "Total annual precipitation is approximately 560 mm."
Use the overall shape to classify the climate. See the climate type guide below.
Climate Types — What to Look For
| Climate Type | Temperature Pattern | Precipitation Pattern | Example Location |
|---|---|---|---|
| Equatorial | High all year (25–30°C), small annual range (<5°C) | High all year (over 2,000 mm total), no dry season; often two rainfall peaks | Manaus, Brazil; Singapore |
| Tropical monsoon | High all year (20–30°C) | Extreme seasonal contrast — intense wet season (June–Sept) and dry season (Oct–May) | Mumbai, India; Dhaka, Bangladesh |
| Mediterranean | Hot dry summer (25–30°C), mild wet winter (8–12°C) | Low in summer (<20 mm/month), higher in winter; total 300–600 mm | Barcelona, Spain; Athens, Greece |
| Maritime temperate | Mild all year; small range (10–15°C); no extreme cold or heat | Moderate, fairly evenly spread throughout year (600–900 mm total) | London, UK; Dublin, Ireland |
| Semi-arid / desert | Very high summer, cool winter; very large annual range (30°C+) | Extremely low all year (<250 mm total); near-zero monthly values | Cairo, Egypt; Phoenix, Arizona |
| Tundra / polar | Very cold all year; most months below 0°C; short warm summer (5–10°C) | Very low all year (100–300 mm), often as snow; no month exceeds 50 mm | Fairbanks, Alaska; Tromsø, Norway |
Worked Example: London Climate Graph
Using the five-step method:
- Hottest month: July at approximately 18°C. Coldest month: January at approximately 4°C.
- Annual temperature range: 18 – 4 = 14°C — a moderate range indicating an oceanic/maritime climate.
- Wettest month: October/November at approximately 65 mm. Driest: April at approximately 37 mm.
- Total annual precipitation: approximately 600 mm, fairly evenly distributed with no pronounced dry season.
- Climate type: Maritime temperate. Evidence: small annual temperature range (14°C), mild winters (above 0°C), moderate precipitation year-round with no strong seasonal concentration.
Examination answer using TACT: "London's climate graph shows a trend of moderately warm summers and mild winters, with a temperature line rising from approximately 4°C in January to 18°C in July — an annual range of 14°C. This small range is an anomaly compared to continental European cities at similar latitudes (Berlin has a range of over 20°C), reflecting London's proximity to the Atlantic Ocean and the moderating influence of the North Atlantic Drift. Comparing the wettest and driest months, October (65 mm) receives approximately 75% more precipitation than April (37 mm), though this variation is relatively modest. The total annual precipitation of approximately 600 mm, evenly spread, classifies London as a maritime temperate climate."
Worked Example: Cairo Climate Graph
Cairo's graph looks dramatically different:
- Hottest month: July at approximately 35°C. Coldest: January at approximately 13°C.
- Annual temperature range: 35 – 13 = 22°C — a large range reflecting an inland, desert location.
- Wettest month: December at approximately 8 mm. Most months show near-zero rainfall.
- Total annual precipitation: approximately 25 mm — extremely arid. Most months record 0–2 mm.
- Climate type: Hot desert / semi-arid. Evidence: near-zero precipitation throughout the year, extreme summer temperatures, large annual temperature range.
Quick Check: A climate graph shows: hottest month July (29°C), coldest January (10°C), wettest month January (90 mm), driest month July (5 mm), total annual precipitation approximately 620 mm. What climate type is this, and give two pieces of evidence from the graph to support your answer.
Mediterranean climate. Evidence 1: Hot, dry summer — July is the hottest month (29°C) but also the driest (5 mm), which is the defining characteristic of a Mediterranean climate where high pressure dominates in summer, suppressing rainfall. Evidence 2: Wet, mild winter — January is cool (10°C) but the wettest month (90 mm), reflecting the influence of low-pressure weather systems in winter when the jet stream shifts southward. The annual temperature range of 19°C (29 – 10°C) and total precipitation of 620 mm are consistent with Mediterranean locations such as Rome, Athens, or parts of California and South Africa. A maritime temperate climate has its precipitation spread more evenly throughout the year — the clear wet winter / dry summer contrast confirms Mediterranean. Award marks for: naming the climate type (1 mark); quoting temperature values with units as evidence (1 mark); quoting precipitation values with units as evidence (1 mark); linking the pattern to a geographical explanation such as pressure systems or distance from sea (1 mark for explanation).
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