Modesto
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Modesto clear sky chart from 2005-11-05 to 2017-08-12.

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
70%
15216
31%
46526
26%
15179
75%
15179
48%
23127

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
63%
716
20%
2440
21%
716
66%
716
32%
1363
January16th to endNight
64%
768
25%
2496
25%
768
67%
768
31%
1463
February1st to 15thNight
61%
699
25%
2249
25%
699
66%
699
32%
1304
February16th to endNight
57%
632
26%
1895
24%
632
63%
632
34%
1122
March1st to 15thNight
60%
720
20%
2059
19%
720
63%
720
33%
1252
March16th to endNight
55%
768
23%
2054
15%
768
61%
768
38%
1242
April1st to 15thNight
54%
719
26%
1799
12%
719
60%
719
41%
1086
April16th to endNight
60%
720
28%
1800
12%
720
66%
720
56%
951
May1st to 15thNight
69%
633
32%
1713
20%
633
73%
633
66%
795
May16th to endNight
70%
375
35%
1496
33%
374
80%
374
57%
538
June1st to 15thNight
71%
360
32%
1440
32%
360
81%
360
61%
500
June16th to endNight
87%
360
40%
1440
49%
360
93%
360
80%
425
July1st to 15thNight
91%
340
37%
1360
47%
340
93%
340
80%
394
July16th to endNight
87%
533
39%
1562
35%
500
89%
500
72%
612
August1st to 15thNight
89%
585
41%
1634
29%
582
91%
582
83%
652
August16th to endNight
90%
700
44%
1750
28%
700
92%
700
87%
753
September1st to 15thNight
90%
660
46%
1650
32%
660
92%
660
84%
727
September16th to endNight
83%
656
47%
1774
40%
656
88%
656
78%
756
October1st to 15thNight
73%
660
33%
1980
32%
660
80%
660
56%
920
October16th to endNight
76%
704
39%
2112
40%
704
81%
704
59%
954
November1st to 15thNight
72%
700
32%
2236
32%
700
77%
700
49%
1079
November16th to endNight
68%
720
28%
2379
27%
720
73%
720
40%
1210
December1st to 15thNight
62%
720
22%
2520
20%
720
69%
720
29%
1467
December16th to endNight
54%
768
22%
2688
20%
768
61%
768
27%
1562

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
6%313212335%66%
47454
Night
7%212212335%65%
46711
TransparencyDay
21%38%19%25%20%
47137
Night
21%39%20%24%20%
46527
SeeingDay
7%415%26%29%16%
5778
Night
8%214%38%32%4
15226

By Month

Percentage Cloud Cover SW (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
14%7%26%32445%7%40%
1495
16th to endDay
16%8%36%5%35%335%39%
1728
February1st to 15thDay
15%5%35%425%35%6%43%
1613
16th to endDay
15%4235%23446%45%
1579
March1st to 15thDay
10%424435%5%5%10%44%
1899
16th to endDay
9%423426%5%5%6%48%
2169
April1st to 15thDay
10%425%31335%7%51%
2149
16th to endDay
7%212213345%66%
2160
May1st to 15thDay
221112245%75%
2234
16th to endDay
311221334471%
2615
June1st to 15thDay
2211112235%75%
2520
16th to endDay
111288%
2520
July1st to 15thDay
112289%
2520
16th to endDay
111112385%
2498
August1st to 15thDay
11111111188%
2231
16th to endDay
11112387%
2100
September1st to 15thDay
111388%
1980
16th to endDay
1111123481%
1854
October1st to 15thDay
3112221335%72%
1650
16th to endDay
5%313222345%66%
1760
November1st to 15thDay
6%32332345%7%57%
1623
16th to endDay
10%7%36%414345%48%
1581
December1st to 15thDay
13%7%36%6%34336%41%
1440
16th to endDay
17%6%26%423347%40%
1536
January1st to 15thNight
12%5%2321335%8%50%
2440
16th to endNight
14%414424346%49%
2496
February1st to 15thNight
14%324323448%48%
2238
16th to endNight
15%31442235%7%50%
1895
March1st to 15thNight
13%324423345%51%
2059
16th to endNight
10%413323448%52%
2054
April1st to 15thNight
9%32232445%6%54%
1799
16th to endNight
4212313345%68%
1800
May1st to 15thNight
1211212226%75%
1713
16th to endNight
311111325%76%
1496
June1st to 15thNight
21111123480%
1440
16th to endNight
111289%
1440
July1st to 15thNight
1122287%
1440
16th to endNight
1111212283%
1669
August1st to 15thNight
1111288%
1643
16th to endNight
112388%
1750
September1st to 15thNight
111290%
1650
16th to endNight
112112384%
1774
October1st to 15thNight
411221233471%
1980
16th to endNight
4112212245%72%
2112
November1st to 15thNight
7%212212236%66%
2236
16th to endNight
8%213324347%58%
2379
December1st to 15thNight
13%5%2332445%6%49%
2520
16th to endNight
18%323323346%48%
2688

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
41%6%14%17%18%2
1495
16th to endDay
46%6%8%17%16%4
1728
February1st to 15thDay
40%6%12%24%12%3
1613
16th to endDay
38%5%13%25%15%1
1579
March1st to 15thDay
33%6%14%24%17%4
1899
16th to endDay
32%8%17%20%18%3
2169
April1st to 15thDay
32%5%12%26%18%4
2149
16th to endDay
19%413%26%28%7%
2160
May1st to 15thDay
12%29%25%36%12%
2234
16th to endDay
15%310%27%30%12%
2619
June1st to 15thDay
13%38%22%28%23%
2520
16th to endDay
6%1113%33%44%
2520
July1st to 15thDay
417%23%62%
2371
16th to endDay
7%128%26%54%
2342
August1st to 15thDay
7%19%29%51%
2215
16th to endDay
5%210%38%43%
2100
September1st to 15thDay
41211%33%46%
1980
16th to endDay
8%1422%38%24%
1854
October1st to 15thDay
13%39%26%26%20%
1650
16th to endDay
20%38%25%29%12%
1760
November1st to 15thDay
25%413%31%21%2
1623
16th to endDay
37%5%12%24%17%2
1581
December1st to 15thDay
45%412%18%16%2
1440
16th to endDay
43%6%14%18%14%2
1536
January1st to 15thNight
32%5%13%25%17%6%
2440
16th to endNight
34%5%12%18%17%11%
2496
February1st to 15thNight
33%411%25%17%6%
2249
16th to endNight
32%5%12%26%19%3
1895
March1st to 15thNight
33%5%12%20%19%7%
2059
16th to endNight
29%6%13%21%19%8%
2054
April1st to 15thNight
28%5%12%26%20%6%
1799
16th to endNight
17%415%22%29%11%
1800
May1st to 15thNight
12%27%23%33%20%
1714
16th to endNight
12%29%29%32%13%
1496
June1st to 15thNight
10%29%21%29%26%
1440
16th to endNight
41211%28%51%
1440
July1st to 15thNight
4127%20%64%
1360
16th to endNight
9%137%22%55%
1562
August1st to 15thNight
5%1112%26%52%
1634
16th to endNight
4210%33%48%
1750
September1st to 15thNight
5%128%29%51%
1650
16th to endNight
7%1219%38%30%
1774
October1st to 15thNight
16%38%22%26%22%
1980
16th to endNight
14%38%23%31%19%
2112
November1st to 15thNight
20%311%28%27%8%
2236
16th to endNight
25%311%26%25%6%
2379
December1st to 15thNight
34%6%13%21%18%6%
2520
16th to endNight
36%415%20%16%5%
2688

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
23%22%23%16%13%
123
16th to endDay
18%318%22%17%19%
256
February1st to 15thDay
18%7%15%17%22%18%
243
16th to endDay
15%7%18%24%19%12%
238
March1st to 15thDay
15%5%21%23%21%12%
270
16th to endDay
11%8%22%30%18%7%
288
April1st to 15thDay
14%13%30%18%13%9%
269
16th to endDay
8%12%24%30%15%8%
270
May1st to 15thDay
46%23%28%24%11%
288
16th to endDay
5%6%17%21%34%14%
330
June1st to 15thDay
37%19%34%26%8%
315
16th to endDay
212%33%39%13%
315
July1st to 15thDay
5%26%40%26%
305
16th to endDay
325%46%24%
327
August1st to 15thDay
36%30%42%16%
300
16th to endDay
5%25%43%24%
268
September1st to 15thDay
428%40%25%
255
16th to endDay
2310%29%30%22%
255
October1st to 15thDay
5%5%16%26%26%18%
255
16th to endDay
8%314%25%29%18%
272
November1st to 15thDay
8%212%14%30%31%
129
16th to endDay
9%414%38%26%6%
83
December1st to 15thDay
25%5%26%23%20%
60
16th to endDay
12%115%25%34%10%
64
January1st to 15thNight
14%210%32%32%6%
720
16th to endNight
15%212%33%28%8%
768
February1st to 15thNight
13%215%34%28%5%
704
16th to endNight
14%319%35%22%4
632
March1st to 15thNight
13%315%35%28%3
720
16th to endNight
12%422%33%25%2
768
April1st to 15thNight
10%424%36%22%1
719
16th to endNight
5%425%33%27%3
720
May1st to 15thNight
3123%41%26%3
634
16th to endNight
4319%42%29%1
375
June1st to 15thNight
3221%46%25%1
360
16th to endNight
110%52%34%
360
July1st to 15thNight
6%54%38%
340
16th to endNight
16%39%48%3
533
August1st to 15thNight
7%47%40%3
585
16th to endNight
6%46%43%2
700
September1st to 15thNight
16%43%46%3
660
16th to endNight
112%37%41%7%
656
October1st to 15thNight
5%115%36%34%7%
660
16th to endNight
4213%32%36%11%
704
November1st to 15thNight
8%113%34%35%6%
700
16th to endNight
9%112%37%31%7%
720
December1st to 15thNight
14%311%39%24%5%
720
16th to endNight
19%316%32%24%2
768
Page generated at 2017-08-13 11:16:47. Version ac04

Copyright 2017 A. Danko


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