Solving the Swiss-Italian lake climate mystery...

[karlbonner82]

It's common knowledge that the Swiss-Italian lakes (Como, Maggiore, Lugano etc.) are renowned for their thousands of tall and vigorous windmill palms- palms that are so well adapted that they have become a serious invasive threat to neighboring forest lands.

However, there are many other palm specimens such as CIDP, Queens, and Washingtonia robusta which also have been seen surviving and maturing near the lake fronts. These palms are less reliable than Trachycarpus in marginal, high-latitude climates such as Portland, Oregon and Seattle, Washington. 

I don't have access to truly reliable climate data for the lake regions of the southern Alps, so I did a simple Google search for “Lugano Switzerland average temperature”.  The results made me scratch my head.  Lugano is at 46°N latitude, roughly the same as Portland. Average temperatures in December-February are nearly identical to Portland and Seattle.  Summer temps are quite similar, except for slightly warmer nights in Lugano. 

The main climatic difference between the Pacific Northwest and the Lake District is seasonal rainfall. Portland is known for very wet winters and equally dry summers, while Lugano has a strong summer monsoon season and somewhat drier winters (though still not all that dry).  I will come back to this point shortly.

Geographically, the lakes are tucked away in the interior of west-central Europe, far from the influence of the Atlantic or the Mediterranean. The large and deep lakes undoubtedly have some moderating influence near the shorelines on cold, clear winter nights.  I could imagine that spots near the lake (say less than ½ mile away), might be about a half-zone milder than they would be with no lake present. 

Still, Portland and Seattle have moderating features of their own:  large urban heat islands plus plenty of water from the lower Columbia River and the Puget Sound.  So when you factor in the similar winter average temperatures and the various cold-buffering features, the three cities ought to have fairly similar hardiness zone ratings.

Yet Mexican fan palms and Canary Island date palms are clearly not reliable in Portland or Seattle climates, despite being on the cusp of zones 8b & 9a.  The arctic freezes we get seem to be a few degrees too cold for a little too long duration. 

Years ago I brought this topic up on another palm forum, wondering why Swiss-Italians can grow more palms than Cascadians.  Most of the thoughts revolved around drier winters in the Lake District, though it doesn't seem like they are dry enough to make a real difference. Perhaps the Alps are more effective than the Cascades at blocking frigid airmasses, or else the moderating effect of the lake is greater than I surmised.

Finally…does anyone here know of detailed weather records for stations near the Swiss-Italian lakes?  If I could dig up records on seasonal minimum temperatures then I could calculate the hardiness zone for lakeside locations. Plus I could look at the duration of cold snaps and daytime temperatures during cold snaps.  These data would paint a clearer picture of exactly what plants must endure each season.

[sped94]

HI!

I can describe you the climate of Lake Garda, which I know quite well.

In winter the days are often sunny and dry. The minimum temperatures are reached on clear nights, when the cold air settles on the ground. However, the lake greatly mitigates this situation: Minimum temperatures rarely drop much below 0°C/32F and maximum temperatures are always above 0°C/32F
Spring is mild and very variable.
The summer is characterized by the presence of the African anticyclone. Days are generally warm and sunny, interrupted only by heat storms during the evening hours. Maximum temperatures are almost always around 30°C/86F
Autumn is mild and rainy.

Below I attach the data relating to rainfall and extreme temperatures (maximum and minimum) for "Torbole sul Garda" from 2016 to 2023

 

[Jack Lord]

Years ago, I spent a few days in Lugano. I too wondered about how these palms were flourishing, but had little information as this was before the Internet. I recall thinking the mountains somewhat resembled those you see in California- a bit on the dry side. They do not look like the lush green forested mountains of the PNW. So I wouild think the dryer winters are the factor. Whatever it is, great town. It's the place that sparked my interest in hardy palms and microclimates.

[jwitt]

6 hours ago, sped94 said:

HI!

I can describe you the climate of Lake Garda, which I know quite well.

In winter the days are often sunny and dry.

Pretty much the opposite of Portland!

 

[karlbonner82]

13 hours ago, sped94 said:

HI!

I can describe you the climate of Lake Garda, which I know quite well.

In winter the days are often sunny and dry. The minimum temperatures are reached on clear nights, when the cold air settles on 

Below I attach the data relating to rainfall and extreme temperatures (maximum and minimum) for "Torbole sul Garda" from 2016 to 2023

 

 

 

Can you send me the link to this weather data?  I'd like to check out a few other cities in the region. 

[RedRabbit]

Climate data for the Vevey and Montreux area on Lake Geneva may be worth reviewing too. They’re known for having a strong microclimate for that latitude.

[RedRabbit]

By the way, I’m not too sure what the limit is for Windmills. I’ve seen them on the Lake Constance and there presumably could be some further north into Germany. 

[sped94]

23 hours ago, karlbonner82 said:

Can you send me the link to this weather data?  I'd like to check out a few other cities in the region. 

https://www.meteonetwork.it/rete/livemap/#

[Axel Amsterdam]

I can’t help you on the climatic data, although i know that certain parts around the lake lugano and lago maggiore don’t go much below -2C in regular winters always combined with positive daytemps. These areas are particularly present on the north/west side of the lakes benefitting from sun exposure on clear winter days. 

Since a lot of experimental planting is done in these areas, perhaps it’s best to let the (unprotected) plants tell the story. This is a very knowledgeable plantsgrower living in the area and documenting all plants throughout the years:

https://www.facebook.com/profile.php?id=100080329200776

[Axel Amsterdam]

As can be seen in one of his posts, the region historically always had a keen botanical interest in taking advantage of the climate 

[karlbonner82]

1 hour ago, Axel Amsterdam said:

As can be seen in one of his posts, the region historically always had a keen botanical interest in taking advantage of the climate 

...So in other words, there was a large enough community of "zone pushing nerds" in the early 20th century, to discover the region's mild climate and exploit it to the hilt. 🧐

[karlbonner82]

On 5/25/2024 at 1:39 PM, sped94 said:

https://www.meteonetwork.it/rete/livemap/#

I checked out this link and got a neat map of current temperatures, but I don't know how to access monthly averages like you did, nor how to select different stations. 

[sped94]

On 5/27/2024 at 7:50 AM, karlbonner82 said:

I checked out this link and got a neat map of current temperatures, but I don't know how to access monthly averages like you did, nor how to select different stations. 

Open the map and click the temperature you interest. then click "sito web", "archivio" and then select the year you want.

[Jack Lord]

On 5/25/2024 at 1:42 AM, RedRabbit said:

By the way, I’m not too sure what the limit is for Windmills. I’ve seen them on the Lake Constance and there presumably could be some further north into Germany. 

I did a year in Heidelberg back in the mid 90s. There are several planted at the base of the mountain where the Philosophenweg begins.

[Flow]

The alps keep away most of the cold arctic air coming in during winter. I live just 150 km north of Locarno but the climate is a completely different one. We often see prolonged freezes (days or even weeks) that are virtually unkown in Ticino. The last major freeze there was in february 2012 when many Phoenix canariensis defoliated completely, even only a few metres away from the lake.

May 2012