Assuming the orders table is named "Orders", the SQL query would be:

```
SELECT CustomerID, COUNT(OrderID) AS NumOrders
FROM Orders
WHERE MONTH(OrderDate) = 1
GROUP BY CustomerID
```

This query uses the MONTH() function to extract the month from the OrderDate column and filters for the month of January. The result is grouped by CustomerID and the COUNT() function is used to count the number of orders made by each customer during that month. The alias "NumOrders" is assigned to this calculated column.
Data una tabella di ordini con colonne OrderID, CustomerID e OrderDate, scrivi una query SQL per trovare il numero di ordini effettuati da ciascun cliente nel mese di gennaio.