Before a forecast exists, you can still estimate how wet a trip will be. This sheet takes the average number of days per month with at least 1 mm of rain, from the climate tables on Wikipedia for Paris, Amsterdam and Rome, and scales it to the length of your stay. The scaling and the pack rule are our own arithmetic, not a forecast.
The sheet
| City | Month | Wet days in the month | Expected wet days, 3-day trip | 5-day trip | 7-day trip |
|---|---|---|---|---|---|
| Paris | April | 8.6 | 0.9 | 1.4 | 2.0 |
| Paris | July | 7.4 | 0.7 | 1.2 | 1.7 |
| Paris | October | 9.5 | 0.9 | 1.5 | 2.1 |
| Paris | December | 11.4 | 1.1 | 1.8 | 2.6 |
| Amsterdam | April | 8.6 | 0.9 | 1.4 | 2.0 |
| Amsterdam | July | 10.9 | 1.1 | 1.8 | 2.5 |
| Amsterdam | October | 12.4 | 1.2 | 2.0 | 2.8 |
| Amsterdam | December | 14.1 | 1.4 | 2.3 | 3.2 |
| Rome | April | 7.4 | 0.7 | 1.2 | 1.7 |
| Rome | July | 2.2 | 0.2 | 0.4 | 0.5 |
| Rome | October | 7.3 | 0.7 | 1.2 | 1.6 |
| Rome | December | 9.4 | 0.9 | 1.5 | 2.1 |
Read a row as “in a typical April in Paris, expect about one wet day in a three-day stay”. Rome in July is the outlier, with fewer than one wet day expected even on a week-long trip; Amsterdam in December sits at the other end.
What to pack
| Expected wet days | Rule of thumb |
|---|---|
| Under 1 | A pocket folder is optional; a hooded jacket will do |
| 1 to 2 | Pack one compact folder, or a hooded jacket if you travel carry-on only |
| Over 2 | Pack a folder and plan an indoor stop for each wet day |
The rule is ours. If you are unsure whether the umbrella or the jacket should win, our umbrella or rain jacket guide sorts it by trip type, and the chance of rain guide explains what a forecast percentage means once the trip is close.
One example
XZVZX and Calm Eden share an owner. Calm Eden’s Europe city break umbrella guide walks through the same three cities with the umbrella-versus-jacket trade-offs. Its Haven Umbrella listing gives a weight of about 390 g, which is the number to compare against a jacket if your bag is tight.
Short version
- Wet-day averages are odds, not a forecast.
- Scale the monthly figure to your trip length, then use the rule.
- Recheck with a real forecast the week before you go.
Sources: the climate tables on the Wikipedia pages for Paris, Amsterdam and Rome, read on 28 October 2026. Product details for the Haven Umbrella come from the seller’s listing.
Common questions
What counts as a wet day in these numbers?
A day with at least 1 mm of rain, as listed in the climate tables on each city's Wikipedia page. A ten-minute shower can make a day count, so the figure is the odds of some rain, not of a washout.
Is this a forecast?
No. These are long-run monthly averages for a city. A real trip can be drier or wetter, so check the forecast the week before you fly.
How do I turn the numbers into a pack decision?
Multiply the monthly wet days by the share of the month you are there, which the table does for 3, 5 and 7 days. Our rule of thumb is below one wet day: optional; one to two: pack a pocket folder; over two: pack a folder and plan an indoor stop for each wet day.
Why not use the percent chance on a weather app?
That tells you about one forecast hour or day. Climate averages tell you what to expect before a forecast exists, such as when you are booking flights.