This is one of the stupid ideas I often have. I make a small observation and think that I can quickly research it and get an answer. But often it turns into a time consuming project. Like this one.
This winter season I had the feeling that it was always raining on weekends, but during weekdays it was dry and good weather. Which was quite annoying for me, because I have only time on weekends to go out and take photos.
To test my observations, I checked the precipitation data provided by the Central Weather Bureau Taiwan. The data used for my small study are only from the weather station Taipei (466920) in Zhongzhen District, near the Presidential Office Building in Taipei City. This station is representative for the area of Taipei City. But not for the outskirts of the city. If you are located outside of Taipei City, then the results might be slightly different. For those who are interested to replicate this, the climate data can be downloaded here.
The first thing was that I only looked at the time period from November 2018 to April 2019. Basically winter and beginning of spring. Then I counted how many of each weekday where rainy days. I did not consider the amount and duration of rain. What I did here was a very basic approach. In reality, duration and amount of rain would influence my decision, if I go out or not. For example, after a short but strong rain shower in the morning, I would go out in the afternoon. But would not leave the house if the whole day is only drizzling rain.
However, the result for the November to April period was surprising. Indeed it rained more often on Sundays and Mondays, but significantly less on Tuesdays and Wednesdays. The difference is remarkable. During this time period there were only six rainy Wednesdays, but 14 rainy Sundays.
Then I thought, this might be just a coincidence, and looked for the entire year from March 2018 to February 2019. I choose this time period because it covers the four seasons spring, summer, autumn and winter. Now the distribution is not so clear anymore. It seems that Wednesday is still the driest day of the week. On the other hand Saturday and Sunday are not the rainiest anymore. Tuesday and Friday are the days where it rained most often.
When looking at a longer time period, in this case from March 2010 to February 2019, then everything starts to average out and no clear trend is visible. This is actually what you can expect. There is no daily preference for rainfall. It looks a little bit, that more rain falls on Fridays. However, I think when looking over an even longer time period, all days will be more or less equally rainy.
Edit on April 19, 2019: The author added the name and location of the weather station from where the data was used for this small study.