Did the solar eclipse affect the local weather? 1


Here on the south coast at Peacehaven near Brighton, today’s (20 March 2015) solar eclipse reached 85% of the sun being blocked by the moon. So did the weather station on the roof of our house detect any variance in weather measurements?

The answer is Yes …but only slightly. Let’s have a look at the 24-hour weather graphs. The green line shows the time of maximum partial eclipse bearing in mind that the maximum (85%) covering of the sun by the moon took place here at 9:35am:

A set of graphs showing various weather metrics. The green line shows the time of maximum partial eclipse.

A set of graphs showing various weather metrics. The green line shows the time of maximum partial eclipse.

The outside temperature and wind are of most interest here. Note a very small dip in the outside temperature and wind chill values at the time of the eclipse (top two graphs). The wind speed change is, again, slight but increases from the moment of the eclipse.

Here is the data. The weather system logs measurements every 5 minutes. Entry 21 is the time of maximum partial eclipse:

A B C D E F
1
Date Time Celsius Fahrenheit windSpeed (mph) windGust (mph) windDir (degrees)
2
20/03/2015 08:00:00 4.27 39.7 7 11 45
3
20/03/2015 08:05:00 4.22 39.6 9 14 45
4
20/03/2015 08:10:00 4.27 39.7 9 14 45
5
20/03/2015 08:15:00 4.38 39.9 6 13 45
6
20/03/2015 08:20:00 4.38 39.9 7 13 22.5
7
20/03/2015 08:25:00 4.33 39.8 9 14 45
8
20/03/2015 08:30:00 4.38 39.9 6 11 45
9
20/03/2015 08:35:00 4.38 39.9 7 12 45
10
20/03/2015 08:40:00 4.38 39.9 7 12 45
11
20/03/2015 08:45:00 4.38 39.9 7 12 45
12
20/03/2015 08:50:00 4.33 39.8 5 11 45
13
20/03/2015 08:55:00 4.44 40 4 8 45
14
20/03/2015 09:00:00 4.5 40.1 5 9 45
15
20/03/2015 09:05:00 4.55 40.2 4 7 45
16
20/03/2015 09:10:00 4.44 40 7 13 22.5
17
20/03/2015 09:15:00 4.44 40 6 11 45
18
20/03/2015 09:20:00 4.44 40 5 11 22.5
19
20/03/2015 09:25:00 4.38 39.9 5 10 22.5
20
20/03/2015 09:30:00 4.38 39.9 6 10 22.5
21
20/03/2015 09:35:00 4.38 39.9 5 9 45
22
20/03/2015 09:40:00 4.33 39.8 6 9 45
23
20/03/2015 09:45:00 4.38 39.9 5 8 45
24
20/03/2015 09:50:00 4.38 39.9 5 10 22.5
25
20/03/2015 09:55:00 4.44 40 5 8 22.5
26
20/03/2015 10:00:00 4.44 40 7 10 22.5
27
20/03/2015 10:05:00 4.5 40.1 5 9 22.5
28
20/03/2015 10:10:00 4.5 40.1 7 11 45
29
20/03/2015 10:15:00 4.55 40.2 6 12 45

he temperature was climbing (as it does most mornings when the sun becomes higher in the sky and provides more heat energy) – but at the moment of the greatest level of partial eclipse it slips back slightly before recovering as the eclipse passes. It’s not much, though: From 40.2F / 4.55C at 9:05am it falls to 39.8F / 4.33C at 9:40am.

It seems that the sudden lack of energy from the sun does affect the weather but by only the smallest amount. Indeed the effect is similar walking from sunshine into shade and detecting that it’s slightly cooler.

 

  • it didn’t even get very dark in central London…