## 4 Conclusions
Future projections show an increase, relative to HIST, of annual average Tmax of 1.9 \({}^{\circ}\)C and 3.7 \({}^{\circ}\)C for MED and LONG, respectively. For Tmin, the values are 1.6 \({}^{\circ}\)C and 3.2 \({}^{\circ}\)C, respectively; these are slightly below those for Tmax, which translates into a slight increase of average daily temperature range. Both temperatures show larger increases from July to October (2.6 \({}^{\circ}\)C and 5.3 \({}^{\circ}\)C for Tmax in July, in MED and LONG, respectively). For HW, the annual average of NDAYS is expected to increase more than 3-fold (38 days) and 6-fold (63 days) in MED and LONG, relative to HIST (10 days), respectively. In individual years, NDAYS in excess of 100 are expected to occur, which represents much of the extended summer (180 days) under HW conditions. In addition, Tmax_ave is expected to increase, on average, from 33.7 \({}^{\circ}\)C in HIST to 34.1 \({}^{\circ}\)C in MED and 34.9 \({}^{\circ}\)C in LONG but with individual HW reaching Tmax_ave values greater than 40 \({}^{\circ}\)C in the future, particularly in LONG. For example, the percentage of HW days with Tmax equal or greater than 37.5 \({}^{\circ}\)C, relative to the total HW days is 8%, 15%, and 23% for HIST, MED, and LONG, respectively. Extremely intense HW with Tmax_ave above 40 \({}^{\circ}\)C occur only in LONG. The annual average of Tmax_sum increases from 358 \({}^{\circ}\)C-day in HIST to of 1270 \({}^{\circ}\)C-day in MED and 2078 \({}^{\circ}\)C-day in LONG with some years registering more than 3000 \({}^{\circ}\)C-day (i.e., equivalent to 85 NDAYS with Tmax of 35 \({}^{\circ}\)C in each HW day). It has been shown in Section 4 that HW similar to the one of 2003, which was considered one the most intense in Lisbon, are expected to be an average HW in LONG climate. Contrary to HIST, the months from July to October have the highest values of NDAYS and Tmax_sum in MED and LONG, with September and October being the highest of all. This change of extreme heat toward the latter months of the extended summer may be critical for water resources, agriculture, and forest fires, since it coincides with the end of the dry season. As mentioned before, other studies have shown that precipitation is also expected to decrease in summer and autumn, in the future, relative to present climate conditions. All these changes must be considered to implement adaptation and mitigation measures to minimize the effects of heat stress in Lisbon. RP estimates of HW measures were calculated for each climate. As expected, the RP of a specific value for the future projections are much reduced relative to HIST. These may be useful for various socio-economic sectors and may be applied either considering climate change (i.e., from HIST to MED and LONG) or for minimized warming if other drastic greenhouse emission scenarios are implemented. As mentioned before, the models used here may not fully account for the amplification of the HW effects by the Urban Heat Island effect. These models have detailed high-resolution land-usespecifications that consider, amongst others, sub-classes or urban surface. However, to the authors' knowledge, none of these models used an urban canopy scheme. A series of simulations with WRF coupled to an urban canopy parametrization constitute a subsequent step to be performed by the authors to determine, more realistically, the local amplification of HW in Lisbon, particularly during the nights of HW days.