Thurso
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Thurso clear sky chart from 2005-11-05 to 2018-03-11.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
32%
15335
13%
49131
9%
15303
38%
15303
17%
35079

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
18%
780
7%
2716
3%
776
23%
776
8%
2172
January16th to endNight
22%
832
10%
2886
6%
832
28%
832
12%
2171
February1st to 15thNight
20%
764
11%
2482
5%
761
28%
761
11%
1897
February16th to endNight
26%
683
14%
2094
8%
683
35%
683
15%
1563
March1st to 15thNight
21%
764
13%
2252
7%
764
28%
764
14%
1728
March16th to endNight
32%
768
20%
2019
10%
768
39%
768
23%
1404
April1st to 15thNight
28%
718
16%
1796
6%
718
32%
718
22%
1316
April16th to endNight
29%
642
17%
1722
7%
642
36%
642
24%
1214
May1st to 15thNight
33%
360
16%
1440
13%
360
43%
360
16%
952
May16th to endNight
37%
375
13%
1497
11%
374
47%
374
18%
964
June1st to 15thNight
38%
360
9%
1440
9%
360
45%
360
15%
981
June16th to endNight
45%
360
9%
1440
12%
360
48%
360
19%
914
July1st to 15thNight
57%
340
13%
1360
19%
340
62%
340
25%
773
July16th to endNight
58%
376
13%
1418
18%
354
61%
354
25%
823
August1st to 15thNight
57%
413
13%
1484
14%
411
60%
411
23%
925
August16th to endNight
55%
723
19%
1869
10%
723
58%
723
36%
1167
September1st to 15thNight
49%
720
15%
1800
7%
720
51%
720
28%
1244
September16th to endNight
50%
717
23%
1950
15%
717
54%
717
32%
1243
October1st to 15thNight
37%
720
17%
2160
12%
720
45%
720
21%
1483
October16th to endNight
28%
768
11%
2420
7%
768
35%
768
15%
1809
November1st to 15thNight
30%
760
17%
2514
12%
760
38%
760
17%
1776
November16th to endNight
21%
780
10%
2730
6%
780
28%
780
10%
2097
December1st to 15thNight
18%
780
8%
2730
4%
780
24%
780
9%
2155
December16th to endNight
15%
832
11%
2912
4%
832
23%
832
9%
2308

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
18%8%36%5%3445%6%32%
49506
Night
18%9%36%5%34446%32%
49300
Cloud CoverDay
18%8%36%5%3445%6%33%
49515
Night
18%9%36%5%34445%33%
49306
TransparencyDay
51%6%11%19%9%1
49193
Night
52%5%11%19%9%
49131
SeeingDay
22%10%27%23%12%3
5997
Night
22%8%29%28%10%
15335

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
23%15%5%9%5%3343420%
1552
16th to endDay
14%14%6%9%6%35%35%424%
1687
February1st to 15thDay
12%15%5%11%8%3444424%
1710
16th to endDay
19%12%6%8%7%3335%426%
1664
March1st to 15thDay
18%11%5%8%6%35%43427%
1933
16th to endDay
17%7%25%5%25%345%40%
2205
April1st to 15thDay
23%9%36%423335%33%
2152
16th to endDay
20%7%36%5%33435%35%
2250
May1st to 15thDay
21%7%37%434346%32%
2511
16th to endDay
20%6%25%5%3445%7%33%
2618
June1st to 15thDay
21%7%26%5%25%5%5%6%29%
2520
16th to endDay
18%5%25%5%36%6%7%8%30%
2520
July1st to 15thDay
13%5%25%5%45%5%7%8%36%
2520
16th to endDay
12%6%26%5%35%6%6%7%35%
2654
August1st to 15thDay
11%6%36%7%35%5%5%7%36%
2463
16th to endDay
10%425%5%345%5%9%43%
2321
September1st to 15thDay
17%4245%3445%7%40%
2160
16th to endDay
16%414423247%47%
2009
October1st to 15thDay
21%8%345%24346%35%
1800
16th to endDay
26%8%47%6%3444425%
1803
November1st to 15thDay
16%9%35%5%35%5%5%7%32%
1670
16th to endDay
25%10%48%5%34345%25%
1560
December1st to 15thDay
22%14%5%9%5%35%335%19%
1560
16th to endDay
23%17%5%8%6%3333420%
1664
January1st to 15thNight
20%16%6%8%6%35%34420%
2716
16th to endNight
14%15%5%9%6%34445%26%
2886
February1st to 15thNight
12%13%6%11%8%45%44424%
2480
16th to endNight
16%12%5%7%6%35%445%29%
2094
March1st to 15thNight
19%11%48%7%34345%26%
2239
16th to endNight
15%8%36%5%3334442%
2019
April1st to 15thNight
25%7%24433445%35%
1796
16th to endNight
19%7%35%423446%37%
1722
May1st to 15thNight
22%7%27%43333436%
1440
16th to endNight
18%6%25%435%5%47%37%
1495
June1st to 15thNight
19%7%35%445%45%7%32%
1440
16th to endNight
16%5%25%325%5%5%8%36%
1440
July1st to 15thNight
11%3145%245%6%8%45%
1440
16th to endNight
9%5%345%35%46%8%44%
1514
August1st to 15thNight
10%5%245%346%7%9%39%
1494
16th to endNight
10%42442446%6%49%
1869
September1st to 15thNight
15%425%6%24446%41%
1800
16th to endNight
15%423423236%49%
1950
October1st to 15thNight
19%6%25%4245%46%38%
2160
16th to endNight
24%8%35%6%34346%28%
2420
November1st to 15thNight
21%8%35%6%24346%32%
2514
16th to endNight
21%11%48%6%34445%24%
2730
December1st to 15thNight
23%14%5%7%5%2444422%
2730
16th to endNight
23%15%5%7%6%3334421%
2912

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
23%14%6%8%6%24335%20%
1552
16th to endDay
14%15%5%9%5%36%446%24%
1687
February1st to 15thDay
14%13%6%11%8%35%445%24%
1710
16th to endDay
20%11%6%7%6%3444425%
1664
March1st to 15thDay
18%12%48%7%35%43426%
1943
16th to endDay
17%7%25%434445%40%
2204
April1st to 15thDay
22%10%35%424335%34%
2152
16th to endDay
20%7%35%5%24346%35%
2250
May1st to 15thDay
20%7%35%6%43446%33%
2511
16th to endDay
19%6%25%5%3445%7%34%
2618
June1st to 15thDay
21%6%35%5%35%45%7%30%
2520
16th to endDay
18%5%25%5%36%6%7%8%30%
2520
July1st to 15thDay
13%425%5%35%5%7%8%37%
2520
16th to endDay
12%5%26%5%35%6%7%8%35%
2654
August1st to 15thDay
10%5%25%5%45%5%6%7%40%
2463
16th to endDay
9%424425%5%5%8%47%
2321
September1st to 15thDay
16%4244345%5%7%41%
2160
16th to endDay
16%423324346%48%
2009
October1st to 15thDay
20%8%25%434345%35%
1800
16th to endDay
25%9%46%6%3444426%
1803
November1st to 15thDay
16%8%46%5%36%45%6%33%
1670
16th to endDay
25%10%47%5%23345%26%
1560
December1st to 15thDay
22%14%5%8%6%45%345%20%
1560
16th to endDay
23%16%6%7%6%2433421%
1664
January1st to 15thNight
20%15%6%8%6%35%43421%
2716
16th to endNight
15%15%48%6%35%45%5%25%
2886
February1st to 15thNight
12%12%6%10%7%46%5%45%23%
2473
16th to endNight
17%11%48%5%35%5%4429%
2094
March1st to 15thNight
20%11%5%8%7%3433427%
2252
16th to endNight
15%9%36%433335%42%
2019
April1st to 15thNight
24%8%33424336%34%
1796
16th to endNight
19%8%26%423445%38%
1722
May1st to 15thNight
22%8%26%32434436%
1440
16th to endNight
18%6%34425%45%6%37%
1495
June1st to 15thNight
19%7%45%5%2446%7%31%
1440
16th to endNight
17%5%15%425%5%6%7%37%
1440
July1st to 15thNight
11%324435%5%6%7%45%
1440
16th to endNight
9%434435%46%8%44%
1514
August1st to 15thNight
10%5%25%5%346%6%9%41%
1494
16th to endNight
10%31442445%7%50%
1869
September1st to 15thNight
15%5%15%6%3445%5%41%
1800
16th to endNight
16%424323335%50%
1950
October1st to 15thNight
19%6%25%433446%38%
2160
16th to endNight
24%9%35%5%34445%28%
2420
November1st to 15thNight
21%8%26%5%33345%33%
2514
16th to endNight
21%11%46%6%35%445%25%
2730
December1st to 15thNight
22%14%5%7%5%3444422%
2730
16th to endNight
23%16%47%6%2443421%
2912

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
67%5%8%13%5%
1553
16th to endDay
60%5%11%14%7%
1687
February1st to 15thDay
62%5%9%17%4
1712
16th to endDay
60%410%13%9%1
1664
March1st to 15thDay
60%5%10%14%7%1
1943
16th to endDay
45%5%9%17%16%5%
2205
April1st to 15thDay
53%37%19%12%2
2152
16th to endDay
51%47%18%14%4
2250
May1st to 15thDay
52%5%6%19%13%1
2511
16th to endDay
48%7%11%19%11%1
2622
June1st to 15thDay
52%6%11%19%8%
2520
16th to endDay
47%8%13%19%9%
2520
July1st to 15thDay
40%8%14%25%11%
2371
16th to endDay
42%10%15%21%9%
2487
August1st to 15thDay
44%9%15%21%9%
2449
16th to endDay
35%8%18%27%9%
2321
September1st to 15thDay
41%7%12%26%12%
2160
16th to endDay
37%6%13%32%9%
2009
October1st to 15thDay
50%5%12%21%10%
1800
16th to endDay
60%7%12%14%5%
1803
November1st to 15thDay
50%7%15%18%7%1
1670
16th to endDay
60%6%11%14%6%
1560
December1st to 15thDay
67%6%12%11%3
1560
16th to endDay
67%5%8%12%6%
1664
January1st to 15thNight
66%5%10%11%4
2716
16th to endNight
60%410%16%7%
2886
February1st to 15thNight
61%410%18%4
2482
16th to endNight
56%5%9%18%10%
2094
March1st to 15thNight
59%48%17%7%1
2252
16th to endNight
46%49%19%16%4
2019
April1st to 15thNight
51%48%19%15%1
1796
16th to endNight
46%5%8%18%17%3
1722
May1st to 15thNight
50%48%16%14%4
1440
16th to endNight
45%6%12%19%13%2
1497
June1st to 15thNight
50%6%11%21%9%
1440
16th to endNight
42%8%12%20%15%
1440
July1st to 15thNight
32%9%13%29%14%
1360
16th to endNight
35%7%16%25%14%
1418
August1st to 15thNight
37%9%19%22%10%
1484
16th to endNight
33%6%17%31%10%
1869
September1st to 15thNight
42%6%12%25%11%1
1800
16th to endNight
37%5%11%34%10%
1950
October1st to 15thNight
46%6%9%25%11%
2160
16th to endNight
56%5%14%17%5%
2420
November1st to 15thNight
52%413%17%9%1
2514
16th to endNight
60%6%11%16%4
2730
December1st to 15thNight
65%5%12%13%4
2730
16th to endNight
66%49%12%6%
2912

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
31%13%25%25%4
90
16th to endDay
29%10%33%21%2
101
February1st to 15thDay
28%22%34%13%
135
16th to endDay
35%12%28%20%2
245
March1st to 15thDay
26%14%33%19%6%
312
16th to endDay
21%12%30%20%10%4
288
April1st to 15thDay
27%17%29%17%8%1
270
16th to endDay
20%14%30%20%12%2
270
May1st to 15thDay
27%10%29%19%8%4
288
16th to endDay
20%12%33%19%11%2
331
June1st to 15thDay
25%7%31%22%11%1
315
16th to endDay
19%9%26%28%14%2
315
July1st to 15thDay
13%6%31%26%17%4
305
16th to endDay
15%323%32%19%5%
326
August1st to 15thDay
13%322%35%18%5%
313
16th to endDay
11%6%21%29%19%11%
332
September1st to 15thDay
17%6%21%19%22%13%
315
16th to endDay
18%7%20%20%20%13%
314
October1st to 15thDay
25%10%23%22%16%2
315
16th to endDay
27%13%28%22%7%
307
November1st to 15thDay
23%11%26%25%11%1
234
16th to endDay
30%18%30%17%3
90
December1st to 15thDay
23%12%40%21%3
90
16th to endDay
35%16%37%10%
96
January1st to 15thNight
28%11%33%22%5%
780
16th to endNight
22%10%33%26%6%
832
February1st to 15thNight
18%10%39%26%5%
764
16th to endNight
25%9%31%27%5%
683
March1st to 15thNight
26%11%33%24%4
764
16th to endNight
18%11%31%27%10%
768
April1st to 15thNight
26%10%30%27%4
718
16th to endNight
23%10%32%25%7%
642
May1st to 15thNight
26%6%26%29%8%1
360
16th to endNight
19%6%30%30%12%1
375
June1st to 15thNight
20%425%39%10%
360
16th to endNight
17%324%38%13%1
360
July1st to 15thNight
9%324%41%20%
340
16th to endNight
10%219%44%21%1
376
August1st to 15thNight
15%215%39%23%2
413
16th to endNight
10%421%38%23%2
723
September1st to 15thNight
18%422%33%20%1
720
16th to endNight
18%5%22%26%23%2
717
October1st to 15thNight
21%7%27%30%13%
720
16th to endNight
27%9%28%26%7%
768
November1st to 15thNight
26%7%28%24%11%
760
16th to endNight
26%14%29%20%8%
780
December1st to 15thNight
30%10%32%21%4
780
16th to endNight
31%10%32%19%41
832
Page generated at 2018-03-12 13:28:11. Version ac04

Copyright 2018 A. Danko


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