## 3 Results and Discussion
### Temperature Trends
In the case of November, the western coastal zone is cloudy and mild, and northern areas are rather cooler than the southern, reaching an average temperature of 17 \({}^{\circ}\)C in some years. The results for this month showed both positive trends (+0.05 \({}^{\circ}\)C year\({}^{-1}\)) and statistical significance in Sacramento and San Joaquin Valley, Sierra Nevada, Los Angeles, San Francisco Bay, Yosemite and Southern Lake Tahoe. Last but not least, December showed a positive trend in most of California, with the exception of the northwest, where it has been noted a negative trend with a decrease of 0.02 \({}^{\circ}\)C year\({}^{-1}\) during the period studied, although it is not statistically significant. In addition, the territories of Sacramento and San Joaquin Valley showed the highest increases with statistical significance (+0.032 \({}^{\circ}\)C year\({}^{-1}\)). As we have previously pointed out, this is a rising concern due to the fact that snowmelt increases in mountain areas probably causing a shortage in water supply in the months to come. Focusing on the seasonal trends (Figure 3), it is especially striking that both summer and autumn have shown statistically significant positive trends (+0.03 \({}^{\circ}\)C year\({}^{-1}\)). The area with statistical significance spreads over the Mojave Desert and Death Valley, supporting the idea mentioned before that the south of California is warming more than the north of the State. In summer, the warming trend increases towards the interior of the State as we move away from the coast, where the trend is very small and statistically insignificant. These results agree with previous studies that have reported a cooling trend. These drop-in average temperatures could be due to a wide range of factors, such as irrigation, coastal upwelling or cloud cover [56; 78]. The increase in temperatures over inland areas increases sea-breeze flow activity [19; 78] lowering the temperatures in coastal zones of the State. The spatial distribution of winter trends allows us to discriminate between two distinct areas: one formed by the territories of the Kamath Mountains and the other by the north of the Cascade Range, where we find a statistically insignificant negative trend. The rest of the territory in this season has shown a positive trend of +0.02 \({}^{\circ}\)C year\({}^{-1}\). It is noteworthy that this value is statistically significant in Sacramento and San Joaquin Valley and the south of Sierra Nevada. The trend in spring has shown clear warming throughout the territory but with slight statistical significance. Finally, the spatial distribution of annual trends represented in Figure 3 reflected clear warming in the territory, +0.015 \({}^{\circ}\)C year\({}^{-1}\), except for the northern area, in the Klamath Mountains, where there is no clear trend. This issue has been addressed previously by [PERSON] and [PERSON] (2016). It can also be observed that this positive trend in the territory is especially large in the south of the State, with statistical significance in the southeast of Sierra Nevada, coinciding with the Valley of Death and much of the Mojave Desert. These results accord with those proposed by [PERSON] et al. (2011) during 1918-2006 for the maximum and minimum temperature trends since both parameters show a significant rising in the southern part of the State. The whole State getting warmer has concerning implications, such as the snow on the mountainous systems of California melting earlier in winter-spring, which is likely to decrease the water supply even further next season [73; 82]. In addition, more heat produces more evaporation and so irrigation farmland would need more water, increasing the lack of fresh water even more. All in all, over the period of study, as can be seen in Figures 2 and 3, no negative statistically significant trends were found in California.