Several years ago I wrote a post about Equinox Marathon weather, summarizing the conditions for all 50+ races. Since that post Andrea and I have run the relay twice, and I’ve run the full marathon three more times (if I include last year’s COVID-19 cancelled race). Despite no official race last year, quite a few people came out to run it in the rain and fog. This post updates the statistics and plots to include last year’s weather data.
Methods and data are the same as in my previous post, except the daily data has been updated to include years through 2020. The R code is available at the end of the previous post.
Race day weather
Temperatures at the airport on race day ranged from 19.9 °F in 1972 to 68 °F in 1969, but the average range is between 34.5 and 53.0 °F. Using our model of Ester Dome temperatures, we get an average range of 29.8 and 47.3 °F and an overall min / max of 16.1 / 61.3 °F up on the Dome. Generally speaking, it will be below freezing on Ester Dome, but usually before most of the runners get up there.
Precipitation (rain, sleet or snow) has fallen on 18 out of 58 race days, or 31% of the time, and measurable snowfall has been recorded on four of those eighteen. The highest amount fell in 2014 with 0.36 inches of liquid precipitation (no snow was recorded and the temperatures were between 45 and 51 °F so it was almost certainly all rain, even on Ester Dome). More than a quarter of an inch of precipitation fell in three of the eighteen years when it rained or snowed (1990, 1993, and 2014), but most rainfall totals are much smaller.
Measurable snow fell at the airport in four years, or seven percent of the time: 4.1 inches in 1993, 2.1 inches in 1985, 1.2 inches in 1996, and 0.4 inches in 1992. But that’s at the airport station. Five of the 14 years where measurable precipitation fell at the airport and no snow fell, had possible minimum temperatures on Ester Dome that were below freezing. It’s likely that some of the precipitation recorded at the airport in those years was coming down as snow up on Ester Dome. If so, that means snow may have fallen on nine race days, bringing the percentage up to sixteen percent.
Wind data from the airport has only been recorded since 1984, but from those years the average wind speed at the airport on race day is 4.8 miles per hour. The highest 2-minute wind speed during Equinox race day was 21 miles per hour in 2003. Unfortunately, no wind data is available for Ester Dome, but it’s likely to be higher than what is recorded at the airport.
Weather from the week prior
It’s also useful to look at the weather from the week before the race, since excessive pre-race rain or snow can make conditions on race day very different, even if the race day weather is pleasant. The first year I ran the full marathon (2013), it snowed the week before and much of the trail in the woods before the water stop near Henderson and all of the out and back were covered in snow.
The most dramatic example of this was 1992 where 23 inches (!) of snow fell at the airport in the week prior to the race, with much higher totals up on the summit of Ester Dome. Measurable snow has been recorded at the airport in the week prior to six races, but all the weekly totals are under an inch except for the snow year of 1992.
Precipitation has fallen in 46 of 58 pre-race weeks (79% of the time). Three years have had more than an inch of precipitation prior to the race: 1.49 inches in 2015, 1.26 inches in 1992 (most of which fell as snow), and 1.05 inches in 2007. On average, just over two tenths of an inch of precipitation falls in the week before the race.
The following stacked plots shows the weather for all 58 runnings of the Equinox marathon. The top panel shows the range of temperatures on race day from the airport station (wide bars) and estimated on Ester Dome (thin lines below bars). The shaded area at the bottom shows where temperatures are below freezing. The orange horizonal lines represent average high and low temperature in the valley (dashed lines) and on Ester Dome (solid orange lines).
The middle panel shows race day liquid precipitation (rain, melted snow). Bars marked with an asterisk indicate years where snow was also recorded at the airport, but remember that five of the other years with liquid precipitation probably experienced snow on Ester Dome (1977, 1986, 1991, 1994, and 2016) because the temperatures were likely to be below freezing at elevation.
The bottom panel shows precipitation totals from the week prior to the race. Bars marked with an asterisk indicate weeks where snow was also recorded at the airport.
Here’s a table with most of the data from the analysis.
|Date||min t||max t||ED min t||ED max t||awnd||prcp||snow||p prcp||p snow|