Frost Dates and Growing Season in Switzerland

If you pickup any gardening book, then the planting schedule is always given in terms of Last Spring Frost Date and First Fall Frost Date. And usually it is available for the most of US cities. However, I could not find information about any of the Swiss cities. The probability of frost or freeze is greatly affected by elevation, the direction of sunlight (north, south, east or west), prevailing winds and other factors.

I searched some information to come to a likely number for the frost date in switerland. Below is the average weather conditions in Zurich. (BBC Weather)

Next we look at sunrise and sunset during the summer months. (Gaisma)

Also to have the optimal placement and orientatiion of the garden, we need to know the path of the sun. This is help in finding the best location in your house so that it is not shaded by some obstructions.

As you can see in the summer months the sun rises north east (about 30 degrees) and then follows the curve. It us never overhead.

Next looking at the insolation recieved, average temperatures and rainfall we find that compared to other locations at the same latitude zurich is comparetively warmer and has more rainfall.

Looking at all this data, one could say the average last spring frost would be around Apr 25 and average first fall frost would be around Oct 20. This gives us nearly 180 days i.e. 25 weeks of growing season. This also means that some of the plants cannot be sowed directly outside in the soil, you have start the seed indoors or buy transplants from the local nursury.