The southern Mexico and Central America (SMCA) region shows a dominant well‐defined precipitation annual cycle. The rainy season usually begins in May and ends in October, with a relatively dry period in July and August known as the mid‐summer drought (MSD); notable exceptions are the Caribbean coast of Honduras and Costa Rica. This MSD phenomenon is expected to be affected as the SMCA experiences an enhanced differential warming between the Pacific and Atlantic Oceans (PO‐AO) towards the end of the 21st century. Previous studies have suggested that this differential warming will induce a strengthening of the westward Caribbean low‐level jet (CLLJ) and that this heightened CLLJ will shift precipitation westwards, falling on the PO instead that within the SMCA region causing a severe drought. In this work we examine this scenario with a new model, the Rossby Center Regional Climate Model (RCA4), for the COordinated Regional climate Downscaling EXperiment (CORDEX) Central America domain, forced with different general circulation models (GCMs) and for different representative concentration paths (RCPs). We consider 25‐year periods as “present conditions” (1981–2005) and “future scenario” (2071–2095), focusing on the “extended summer” season (May–October). Results suggest that in the future the spatial extension of the MSD will decrease and that in certain areas the MSD will be more intense but less frequent compared to present conditions. Also, the oceanic differential warming, the intensification of the CLLJ, and the reduction in regional precipitation in the future scenario, suggested by previous works, were verified in this study.

One simple way to estimate the relationship between air temperature and the energy needed for heating and cooling is to use the concept of degree day. Cooling degree days (CDD) and heating degree days (HDD) are indicators of the energy required to reach comfort levels and are related directly to energy demands. Therefore, using a novel approach, we examine the current conditions and future projections in degree days over Mexico using observations (Livneh and CPC), ERA5 reanalysis, and simulations from the Regional Climate Model (RegCM4). The RegCM4 experiments were driven by different General Circulation Models for two Representative Concentration Pathways scenarios. We consider three 20-year periods as “present conditions” (1995–2014), “near-future conditions” (2041–2060), and “far-future conditions” (2080–2099). The results suggest that in the future, under the lowest radiative forcing scenario there will be a smaller increase (decrease) in CDD (HDD) for the far-future, as compared to the near-future. This could represent the model’s response to the peak of radiative forcing at mid-century and its subsequent decline. For the highest radiative forcing scenario, we found a greater increase (decrease) in CDD (HDD) for the far-future, which could be explained by the response of the RegCM4 to the warming increase projected for 2100.

The objective of this research was to analyze the temporal patterns of monthly and annual precipitation at 36 weather stations of Aguascalientes, Mexico. The precipitation trend was determined by the Mann–Kendall method and the rate of change with the Theil–Sen estimator. In total, 468 time series were analyzed, 432 out of them were monthly, and 36 were annual. Out of the total monthly precipitation time series, 42 series showed a statistically significant trend (p ≤ 0.05), from which 8/34 showed a statistically significant negative/positive trend. The statistically significant negative trends of monthly precipitation occurred in January, April, October, and December. These trends denoted more significant irrigation water use, higher water extractions from the aquifers in autumn–winter, more significant drought occurrence, low forest productivity, higher wildfire risk, and greater frost risk. The statistically significant positive trends occurred in May, June, July, August, and September; to a certain extent, these would contribute to the hydrology, agriculture, and ecosystem but also could provoke problems due to water excess. In some months, the annual precipitation variability and El Niño-Southern Oscillation (ENSO) were statistically correlated, so it could be established that in Aguascalientes, this phenomenon is one of the causes of the yearly precipitation variation. Out of the total annual precipitation time series, only nine series were statistically significant positive; eight out of them originated by the augments of monthly precipitation. Thirteen weather stations showed statistically significant trends in the total precipitation of the growing season (May, June, July, August, and September); these stations are located in regions of irrigated agriculture. The precipitation decrease in dry months can be mitigated using shorter cycle varieties with lower water consumption, irrigation methods with high efficiency, and repairing irrigation infrastructure. The precipitation increase in humid months can be used to store water and use it during the dry season, and its adverse effects can be palliated with the use of varieties resistant to root diseases and lodging. The results of this work will be beneficial in the management of agriculture, hydrology, and water resources of Aguascalientes and in neighboring arid regions affected by climate change.