Heat Wave – What it does to cows' milk production in dairy farms that intensively cool the cows in the summer

A relatively long heat wave swept through Israel and the Middle East region in mid-August 2025. As expected, reports were received from various regions of the country of a significant decrease in milk yield per cow. A previous review published on the association's website characterized the decrease in milk production following the heat wave. The purpose of the current article is to examine the effect of the increase in cows' heat load during the heat wave period and after it ended, and to examine whether the cows returned to their previous production. In this work, we characterized the climatic changes throughout the heat wave, and also compiled data regarding the extent and duration of the decrease in daily milk yield per cow.

This article presents data on heat loads and milk production in different climate regions of Israel:

The following figures show the minimum and maximum temperatures and daily milk yield per cow during the entire month of August 2025 in the different regions. Blue line represents T min. Orange line represents T Max. and Yellow line represents per cow daily milk production.

As can be seen in the various illustrations, the heat wave began around 7.8 and lasted until 17.8. Milk production returned to near pre-decline levels a few days later, around 22.8.

In order to be able to compare the different regions, we have summarized the main data in the following two tables.

 

From the information presented in the two tables, the following insights can be reached:

-  The minimum temperature at the peak of the heat wave was 6°C higher than the temperature before the heat wave began and did not differ significantly between the different regions.

-  The maximum temperature at the peak of the heat wave was 3 to 8 degrees higher than the temperature before the heat wave began. The largest increase was recorded in the mountains and Jordan valley regions (mostly inland), and the lowest in the coastal region (apparently due to the moderating effect of the sea).

-  The decrease in milk yield at the peak of the heat wave was steady, ranging from 4 kg of milk per cow per day in the Desert, 5 kg per day in the coastal, and 6 kg per day in the others. The smaller decrease recorded on the coast can be explained by the moderating effect of the sea, and in the Desert, by the possibility of more intensive implementation of cooling systems in farms from this region.

-  The most important point for us is the extent of milk loss caused by the heat wave. We see in all evaluated regions that milk yield returns to the initial level before the heat wave, within about a week of its end. This is most probably due to the fact that all farms in Israel implement intensive cooling means and probably these are not sufficient when an extreme heat wave occurs. Assume an average loss per cow per day of 4 kg of milk during the period affected by the heat wave (about 15 days), then the loss per cow will be about 60 kg, which is a negligible amount in relation to the annual yield per cow of above 12,000 kg. When quantifying the economic loss to the dairy farm, it must be taken into account that part of the loss of income due to the decrease in milk production is "offset" with a decrease in food expenses, following the decrease in consumption.

- What was presented in this article refers to the effect of the heat wave on milk production only, and does not include other effects such as damage to the health and fertility of the cows.

-  In conclusion, we believe that the fact that cows in Israel are intensively cooled allows them to better overcome severe heat waves, recover milk production relatively fast, and minimize losses.