During the month of May 2013, Denver, CO’s (link updated monthly) temperatures were 0.8°F above normal (57.9°F vs. 57.1°F). The maximum temperature of 88°F was recorded on the 17th while the minimum temperature of 19°F was recorded on the 2nd. Here is the time series of Denver temperatures in May 2013:
Figure 1. Time series of temperature at Denver, CO during May 2013. Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]
In comparison to March and April 2013, May 2013 brought much less extreme weather to the Denver area. After a cold start to the month, there was a general regime change that allowed high pressure to dominate in the middle and at the end of the month. This high pressure brought warmer than average temperatures, which offset the early month cold snap.
Precipitation was lighter than normal during May 2013: only 0.82″ precipitation fell at Denver during the month instead of the normal 2.12″. Precipitation is a highly variable quantity though. The west side of the Denver Metro area received higher than normal precipitation during the same time period.
Precipitation in the past couple of months alleviated some of the worst drought conditions in northern Colorado. The link goes to a late April 2013 post; further relief occurred in May with regular rain events. All of Colorado continues under at least some measure of drought in early June 2013. The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.
I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects. This series of posts takes a very different look at conditions. Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale. The interannual variability I’ve shown above is a part of natural change. Climate change influences this natural change – on long time frames. The climate signal is not apparent in these figures because they are of too short duration. The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years. The most recent “normal” values cover 1981-2010. The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values. The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.