RAIN PROBABILITY WORKSHEET
Learning Cadence | Original exercise | 31 October 2026

FORECAST LABELS
Provider:
Location named in forecast:
Time interval and time zone:
What event counts as rain:
Probability:
Amount and timing fields, separately:

PRACTICE
A fictional NWS point forecast gives a 40% chance from noon to 6 p.m.
Does it promise 2.4 wet hours? Why?
Does it promise exactly 40% of the park gets rain? Why?
What does it actually say?

ANSWER CHECK
No: probability is not duration.
No: point probability is not an exact area map.
A 40% chance of precipitation at or above the provider threshold at the point during the period. Both wet and dry outcomes remain possible.

TRANSFER
Two hours each show 40%. In 100 equally weighted scenarios, the same 40 are wet in both hours. How many have rain in at least one hour?
Answer: 40, not 80. If different groups of 40 were wet in each hour with no overlap, the answer would be 80. Hourly values alone do not tell you the overlap.

Use current official forecasts and warnings for actual plans. This is a learning exercise, not weather advice.