How do you read a weather radar? Weather radar displays precipitation intensity using color codes – green shows light rain, yellow indicates moderate rain, red means heavy rain, and purple/pink shows very heavy rain or hail. The movement and patterns help predict where weather is heading.
Understanding how to read weather radar is one of the most valuable skills for staying safe and planning your day. Whether you’re checking if it’s safe to drive, planning outdoor activities, or monitoring severe weather, knowing how to interpret radar imagery gives you real-time information about what’s happening right now.
What is weather radar and how does it work?
Weather radar works by sending out pulses of electromagnetic energy. When these pulses hit precipitation (rain, hail, or snow), some energy bounces back to the radar. The radar measures:
- How much energy returns – indicates precipitation intensity
- How long it takes to return – shows distance from radar
- Changes in the return signal – can indicate wind speed and direction
This creates the colorful images you see on weather apps and websites.
What do the colors mean on weather radar?
Weather radar uses a standard color scale to show precipitation intensity:
Light precipitation:
- Light blue/green: Very light rain (drizzle) – 0-5mm per hour
- Green: Light rain – won’t need an umbrella but might get damp
Moderate precipitation:
- Yellow: Moderate rain – 5-10mm per hour – you’ll want an umbrella
- Orange: Moderate to heavy rain – 10-25mm per hour
Heavy precipitation:
- Red: Heavy rain – 25-50mm per hour – poor visibility, hazardous driving
- Dark red: Very heavy rain – over 50mm per hour
Severe precipitation:
- Purple/Pink/White: Extremely heavy rain, large hail, or very intense storms – dangerous conditions
Different weather services may use slightly different color schemes, but the progression from green (light) to red/purple (heavy) is universal.
How can you tell if a storm is coming toward you?
To determine if weather is heading your way:
- Check the radar animation – Most weather radars have a “play” button showing movement over the last 30-60 minutes
- Look at the direction – Weather systems generally move in consistent directions
- Note the speed – Fast-moving systems arrive quickly; slow systems may stall
- Use the loop – Watch 4-5 frames to see the clear direction of movement
In Australia, weather typically moves from:
- West to east (most common)
- Northwest to southeast (cold fronts)
- Northeast to southwest (east coast lows)
What does a severe thunderstorm look like on radar?
Severe thunderstorms have distinctive radar signatures:
Hook echo: A hook-shaped feature indicating possible rotation (tornadoes) Bow echo: Bow-shaped line indicating damaging straight-line winds Intense red/purple cores: Very heavy rain and likely large hail Distinct cell structure: Isolated, circular intense areas Sharp boundaries: Clear edges between intense and light precipitation
If you see these features:
- Take warnings seriously
- Seek shelter immediately
- Stay away from windows
- Monitor official warnings
How do you read radar rain intensity?
Radar rain intensity is measured in millimeters per hour:
- 0-2mm/hour: Light rain – you might not even need an umbrella
- 2-10mm/hour: Moderate rain – steady rainfall, puddles forming
- 10-25mm/hour: Heavy rain – poor visibility, hazardous roads
- 25-50mm/hour: Very heavy rain – flash flooding possible
- 50mm+/hour: Extreme rainfall – dangerous flash flooding likely
For reference, 25mm of rain in an hour is considered heavy enough to cause localized flooding.
What’s the difference between radar and satellite imagery?
Weather radar:
- Shows precipitation (rain, hail, snow)
- Updates every 6-10 minutes
- Shows intensity and movement
- Only shows what’s actively raining
Satellite imagery:
- Shows clouds from space
- Updates every 10-30 minutes
- Shows cloud types and patterns
- Shows clouds even if not raining
Use radar for immediate precipitation impacts, satellite for broader weather patterns and cloud development.
How accurate is weather radar?
Weather radar is highly accurate for:
- Current precipitation location (within 1-2km)
- Precipitation intensity
- Movement direction and speed
- Short-term forecasting (next 1-2 hours)
Radar has limitations:
- Can’t see behind mountains or hills (beam blockage)
- Loses accuracy far from radar site (beyond 200-250km)
- May miss very light rain
- Can show “ground clutter” near the radar as false precipitation
Always use radar in combination with official forecasts and warnings.
How far ahead can radar predict rain?
Weather radar is best for nowcasting – predicting weather for the next 0-2 hours. By watching radar loops, you can reasonably predict:
- 10-30 minutes ahead: Very reliable
- 30-60 minutes ahead: Reliable for existing systems
- 1-2 hours ahead: Reasonably accurate for established patterns
- Beyond 2 hours: Less reliable, use forecasts instead
For longer-term predictions, traditional weather forecasts are more accurate than extrapolating from current radar.
What does it mean when radar shows a “rain shadow”?
A rain shadow on radar appears as an area with less precipitation directly behind higher terrain. This occurs because:
- Mountains force air upward on the windward side
- Air cools and drops moisture as rain
- Drier air descends on the leeward side
- Less moisture available for precipitation
Areas in rain shadows typically receive significantly less rainfall than nearby areas not sheltered by mountains.
How do you use radar for planning outdoor activities?
For immediate activities (next 1-2 hours):
- Check current radar for precipitation location
- Watch the animation loop (30-60 minutes)
- Estimate time until rain arrives
- Check intensity – light rain might be tolerable, heavy rain isn’t
For activities later today:
- Check radar for developing systems
- Review the forecast for timing
- Monitor radar regularly as event approaches
- Have backup plans ready
Pro tip: Check radar 30 minutes before leaving for outdoor activities.
What’s the best weather radar app for Australia?
Bureau of Meteorology (BOM) Weather app – Official source:
- Free and reliable
- Real-time radar updates
- Official warnings integrated
- Multiple radar types available
Other features to look for:
- Animation/loop function
- Location-based alerts
- Lightning detection
- Radar + satellite overlay
The BOM app is recommended because it’s the official source and includes warnings directly from meteorologists.
How do you read rainfall totals on radar?
Many radar displays show accumulated rainfall over periods:
- 1-hour totals: Shows recent heavy rain areas
- 24-hour totals: Indicates areas with significant rainfall
- Since 9am totals: Standard daily measurement period
Color scales for totals differ from intensity:
- Lighter colors: 5-20mm
- Medium colors: 20-50mm
- Dark colors: 50-100mm
- Darkest: 100mm+
Check the scale/legend as different services use different ranges.
What does “clear air mode” mean on radar?
Clear air mode is a radar setting that’s more sensitive and can detect:
- Very light precipitation
- Dust and smoke
- Birds and insects
- Wind patterns in clear air
This mode is useful for:
- Detecting storm initiation
- Tracking smoke from fires
- Identifying wind patterns
- Monitoring very light rain
Standard mode filters out these weaker signals to focus on precipitation.
How can you tell the difference between rain and hail on radar?
Hail typically appears on radar as:
- Very intense returns (bright red/purple/white)
- Distinct, elevated cores within storms
- Often shows up stronger than surrounding rain
- May create “three-body scatter spike” (radar artifact extending from storm)
Dual-polarization radar (used by BOM) can differentiate hail from rain more accurately by analyzing the shape of returned signals. Look for warnings specifically mentioning hail rather than just radar colors.
What should you do if radar shows severe weather approaching?
Immediate actions:
- Check official severe weather warnings (BOM website/app)
- Bring outdoor items inside (furniture, toys, trampolines)
- Move vehicles under cover if hail possible
- Charge phones and devices
- Identify safe shelter location indoors
- Stay away from windows
- Avoid travel if possible
Don’t rely on radar alone – always check official warnings for:
- Specific hazards expected
- Timing information
- Safety advice
- Updates as situation evolves
Where can you access weather radar for free?
Australia:
- Bureau of Meteorology: bom.gov.au/australia/radar
- BOM Weather app (iOS/Android)
- Weatherzone (uses BOM data)
Free radar features:
- National radar composite
- Individual radar sites
- 30-60 minute loops
- Different display modes
Premium services may offer:
- Longer loops
- Higher resolution
- Additional overlays
- Extended forecasts
The free BOM radar is comprehensive and sufficient for most users.
Common weather radar mistakes to avoid
❌ Assuming all green/yellow areas are actively raining – Check the timestamp ❌ Extrapolating too far ahead – Radar is reliable for 1-2 hours max ❌ Ignoring official warnings – Radar doesn’t replace meteorologist warnings ❌ Not checking the radar scale – Different services use different scales ❌ Relying only on radar – Use with forecasts and satellite imagery ❌ Misinterpreting ground clutter – Areas near radar may show false returns
Understanding weather radar empowers you to make informed decisions about your safety and activities. Combine radar with official forecasts and warnings for the most complete picture of current and approaching weather.