Rain Odds™

The horizontal bar shows the Rain Odds spread. The three markers on that bar are:

• P10 — drier-end outcome (only 10% of model runs are lower).
• P50 — the median ("most likely") value; half the runs are higher, half lower.
• P90 — wetter-end outcome (only 10% of runs are higher).

How to read the Rain Odds bar:

• Narrow band: markers clustered → models agree, higher confidence.
• Wide band: markers spread out → models disagree, lower confidence.
• P50 off-center: risk skew. – Closer to P10 → more upside (greater chance of heavier rain). – Closer to P90 → more downside (greater chance it ends up drier).

The single best number to plan around. Works well when the bar is narrow; be more cautious when it's wide.

About 80% of likely outcomes fall between these. Outside this range is possible but lower probability.

Shows the Rain Odds probability of surpassing common thresholds (e.g., 5 mm, 10 mm, 25 mm). Useful for weighing risk of heavy rain.

Rain Odds™ forecasts are grouped into overlapping windows: – 12h / 24h → short-term operational calls – 48h / 72h → medium-range planning

All Rain Odds numbers are liquid water equivalent (mm or inches). In cold weather, convert to snowfall depth:

• Wet snow (~0 °C): 1 mm ≈ 0.5–1 cm
• Typical snow: 1 mm ≈ 1 cm
• Cold/fluffy (≤ −10 °C): 1 mm ≈ 1.5–2 cm

Example: Rain Odds P50 of 10 mm → ~10 cm average snow, or up to 15–20 cm in very cold conditions.

Unlike traditional forecasts that give you a single number (like "10 mm expected"), Rain Odds™ shows you the full range of possibilities from multiple weather models. This helps you understand not just what's most likely, but also what could happen if conditions change.

Rain Odds™ shows area-wide patterns but generally doesn't capture local thunderstorms or convective activity. Individual storms can dump significant rainfall in small areas that won't show up in these ensemble forecasts. During thunderstorm season, some locations may receive much more rain than predicted here due to storm cells passing overhead.

For the most complete picture, check the Rain Odds™ alongside:

• Traditional weather forecasts — for storm warnings and detailed conditions
• Weather radar — to track approaching storms and current precipitation
• Local observations — your own experience with local weather patterns

Think of Rain Odds™ as your "big picture" tool for planning, while radar and local forecasts help with immediate decisions.

Rain Odds™ excels at predicting:

• Large-scale weather systems (fronts, low pressure systems)
• Multi-day precipitation trends
• General wet/dry patterns for planning field work
• Seasonal precipitation (rain or snow)

It's less accurate for:

• Pop-up thunderstorms and convective rainfall
• Very localized precipitation
• Exact timing of rain start/stop (use radar for this)

Use the P50 (most likely) value for general planning, but consider the full range:

• If you can't afford to get wet: Consider the P90 value (worst case)
• If a little rain won't hurt: The P50 value is your best bet
• If you need rain: Look at the P10 value (driest scenario)

The timestamp shown on Rain Odds™ indicates when the weather models started running, not when the data becomes available. These complex models take significant time to process billions of calculations across North America.

Environment Canada's ensemble models run 4 times daily:

• 00Z (00:00 UTC) - 6:00 PM CST / 7:00 PM CDT
• 06Z (06:00 UTC) - 12:00 AM CST / 1:00 AM CDT
• 12Z (12:00 UTC) - 6:00 AM CST / 7:00 AM CDT
• 18Z (18:00 UTC) - 12:00 PM CST / 1:00 PM CDT

Times shown for Central Time (Manitoba). Adjust for your timezone.

Important: Data typically becomes available 3-5 hours after the model run starts. Here's why:

• Models take 2-3 hours to complete their calculations
• Data must be quality-checked and processed
• Files are compiled and distributed to servers
• System load and technical issues can add delays

For example, the 00Z run (7:00 PM CDT) typically becomes available between 10:00 PM and midnight CDT.

For the freshest Rain Odds™ in Central Time, check around:

• Morning (10-11 AM) - Gets the 12Z run from early morning
• Afternoon (4-5 PM) - Gets the 18Z run from noon
• Late evening (10-11 PM) - Gets the 00Z run from evening
• Early morning (4-5 AM) - Gets the 06Z run from overnight

Understanding this timing helps you:

• Know when to check for truly new data (not just refresh the same forecast)
• Understand why a "6 PM forecast" isn't available until 10 PM
• Plan your decision-making around data availability
• Avoid frustration from checking too early for updates

Rain Odds™ automatically checks for new data every 5 minutes while you have the page open. When fresh data arrives, you'll see a notification and the forecast will update automatically. No need to keep refreshing manually!