Scotland is a fairly wet country as a whole, but Edinburgh is actually its driest city on average. What you tend to find here in Scotland is that although there is a lot of rain overall as far as Scotland as a whole is concerned, the vast majority of that tends to occur in the west of Scotland.
The reason for that is due to the fact that the prevailing winds are usually from the SW on average, and also due to the fact that Scotland has a lot of hills and mountains. This enhances the rainfall in the west due to the orographic effect as that moist air from the SW meets those hills and mountains, and is forced to rise over them as a result.
That uses up a lot of the moisture which that air mass contains so that on the other side of those hills and mountains, the air then dries out and warms up as it descends. One effect of this is the Fohn Effect which even in the middle of winter, can easily result in temperatures rising above 15°C in the Moray Firth area in NE Scotland. The other effect of this is that you also have a rain shadow effect on that leeward side of those hills and mountains which then results in it being a lot drier there.
On that front, Edinburgh is well protected by the Pentland and Lammermuir Hills to our south, and other hills to our north over in the Fife and Tayside regions. Because of our position at the eastern end of the Forth Clyde Valley, showers within a polar maritime or returning polar maritime westerly or WSW air stream can filter through that to reach us here in Edinburgh, but we are generally quite well sheltered overall from winds coming from most directions. That in turn causes it to be drier here overall than in most other parts of Scotland.
The only reason why this month has been so wet here is because the main centres of low pressure have been passing right over here just recently and therefore, acting as a convergence zone where big showers and thunderstorms can then develop which then often produce a lot of rain in a very short space of time.
Originally Posted by: johncs2016