The purpose of this article is to present the multi-aspect study led by the ClimXtreme research network of a dry and hot compound event: the European summer of 2018, with a special focus on Germany. The authors succeed in showing the importance of such a multi-faceted analysis in understanding the drivers and dynamics of such dry and hot compound events. The science presented here is sound, and the article is well written.

However, I believe that the authors should have presented another case study (even if more local). Indeed,  this is a long and dense article, as the authors look at different aspects of this compound event, for a case study that has already been intensively documented on different aspects by various publications: exceptionality (e.g. NOAA Global climate report and Met Office report for summer 2018), predictability and drivers (e.g. Dunstone et al. 2019; McCarthy et al., 2019), drought (e.g. Toreti et al. 2019; Peters et al. 2020), dynamics (e.g. Kornhuber et al. 2019; Drouard et al. 2019; Sousa et al. 2019; Li et al., 2020; Spensberger et al. 2020), attribution (e.g. World Weather Attribution Project, 2018; Vogel et al., 2019, Hari et al., 2020). In addition, it has already been regarded as a compound event by previous studies (e.g. Bastos et al., 2021). As the authors point out along the text, most of the findings shown by the authors were already evidenced in previous scientific papers. I understand the argument of the authors on the exceptionality of such a large-scale, persistent, and intense compound event, but I find the paper very long and dense and to me it does not show any substantial new insight on this widely documented compound event. The authors should reduce the length of the paper or better justify the necessity of such a study for the 2018 compound dry and hot event and its added value.

Additional specific comments:

• The data sub-section is very dense and long. Maybe it would benefit of an italic title for each paragraph to quickly find the piece of information needed.
• Lines 190-197: the computation of the 90^th percentile differs for the two heatwave indices?
• Sub-section 2.2.2: I am not sure that three drought indicators are necessary as the purpose of the study is not to compare drought indices or to deeply evaluate the 2018 drought. Mentioning and showing only the SPEI is sufficient to evidence the occurrence and intensity of the drought, as the SPEI is a widely used drought index that considers both precipitation and evapo-transpiration. The SPI is not shown in the main body and does not bring any additional information. And the results shown with the climate network approach could be shown in another way with the SPEI. Showing only one drought indicator would contribute to lighten the text.
• Lines 230-232: The way the blocking index is computed is not clear. Is it a “hybrid” index that looks for an inversion of the Z500 meridional gradient and a strong Z500 anomaly? Are there any spatial and temporal constraints?
• Line 259: are the soil moisture LPJmL simulations absolutely necessary for the paper? It would also contribute to reduce the length of the paper.
• Figures 1d and 1e: you could plot the SPEI value only when it is below the drought threshold.
• Lines 364-365: could you show the thermopluviogram for the Scandinavian region as well?
• Figure 4: Could you show the NAO index for this season as you do for the blocking index?
• Lines 487-490: You should also cite Dunstone et al. 2019: they studied the predictability of this summer season and evidenced the role of this tripole.
• Lines 490-496: The lack of precipitation is also shown in Toreti et al. 2019.
• Lines 504-506: Add a citation.
• Sub-section 3.4: you should cite Vogel et al. 2019 in this sub-section
• Lines 655-656: Cite Dunstone et al. 2019.

Technical corrections:

• Line 468: the closing parenthesis is missing.
• Figure A2, line 702: should be “(b)” instead of “(c)”.

Reference:

Dunstone, N., Smith, D., Hardiman, S., Eade, R., Gordon, M., Hermanson, L., Kay, G. and Scaife, A., 2019. Skilful real‐time seasonal forecasts of the dry Northern European summer 2018. Geophysical Research Letters, 46(21), pp.12368-12376.

General comments:

Firstly, I congratulate the authors for a very well organized and presented manuscript. It must be noted that it is not always easy to summarize and present such a multidisciplinary work, spanning different approaches, and the authors were able to provide this in a very clear and organized way, and furthermore, in a relatively concise way, which is also not easy. The quality of the writing is very good, thus very clear for the reader, and the text avoids being too “heavy”, so being easy to follow.

The manuscript is well structured, with the Abstract and Introduction stating in a clear way the motivation and objectives of the work. The same is valid for the Methods, which are presented in a sound way, providing, as said before, a clear structure of the work flow, despite the complexity of the multidisciplinary approach.

As a consequence, I believe the manuscript is very close to a format suitable to be published. Accordingly, I have just some small comments, which could enhance some small parts/sections. Besides that, I have only a few minor comments regarding one or two less clear sentences and/or typos.

Specific comments:

- L58-60: While I understand the idea in this sentence, I find it presented not in the best way. I would probably suggest the authors to be more specific regarding this specific event.

- L286: How did the authors estimate the impact and potential loss of confidence from regridding the ERA5 data?

-L309-311: Why this specific timeframe?

- Regarding feedbacks between soil moisture deficit and heatwave amplification, while the presented material and evidence is in my point of view more than sufficient for this multidisciplinary approach, I would probably appreciate some more discussion on the soil desiccation mechanisms, and the approaches/methodologies to address this relatively complex subject, which have for example been very well discussed (e.g. 2010 european HWs) in works such as the ones from Miralles et al. (2014), or Schumacher et al. (2019).

- L430-434: I understand the local/regional description, however this may be somehow slightly misleading. I am not sure if extreme heat and temperature records in NW Iberia related with the advection of a Saharan air mass could or not be completely defined as “regional”. In particular, the role of the advection of desertic air masses (associated with ridge activity) for Iberian heatwaves has been discussed in Sousa et al (2019).

Minor comments:

- L467 (and other instances): “warm conveyor belt”

- Fig.6 seems a bit too stretched vertically

- L547/551: I suggest adding here in brackets the period considered for ERA5 and “recent climate”

- L618: has warmed ~2ºC since when / compared to?

- L662: please put the mentioned UK record into context (very briefly of course, dates, etc.)