Spanish Fork
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spanish Fork clear sky chart from 2005-11-06 to 2024-11-03.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	6% 8% 2 6% 4 4 4 3 5% 7% 52%	100815
	Night	6% 9% 3 6% 4 3 4 3 5% 6% 50%	98430
Transparency	Day	31% 6% 10% 18% 21% 14%	100580
	Night	33% 6% 10% 20% 19% 11%	98254
Seeing	Day	9% 10% 25% 33% 19% 4	14725
	Night	11% 5% 18% 41% 24% 3	25308

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 18% 5% 13% 5% 4 4 3 5% 6% 29%	2858
	11th to 20th	Day	10% 21% 5% 13% 4 3 3 3 3 5% 29%	2860
	21st to end	Day	8% 15% 6% 10% 5% 3 3 2 4 5% 38%	3146
February	1st to 10th	Day	10% 14% 4 9% 6% 4 3 3 5% 6% 36%	1710
	11th to 20th	Day	10% 14% 4 8% 4 4 4 4 5% 6% 37%	1734
	21st to end	Day	7% 15% 5% 9% 4 5% 4 3 5% 6% 36%	1570
March	1st to 10th	Day	4 14% 5% 9% 5% 4 4 4 5% 8% 38%	3379
	11th to 20th	Day	5% 11% 3 8% 5% 4 4 4 6% 7% 43%	3490
	21st to end	Day	8% 18% 5% 11% 6% 6% 5% 4 6% 6% 24%	3825
April	1st to 10th	Day	9% 10% 3 6% 5% 4 5% 4 5% 6% 43%	2109
	11th to 20th	Day	7% 11% 3 8% 5% 4 4 3 5% 6% 44%	2371
	21st to end	Day	8% 9% 2 6% 3 4 3 3 5% 6% 49%	2470
May	1st to 10th	Day	8% 11% 2 6% 4 5% 5% 4 6% 8% 40%	4110
	11th to 20th	Day	5% 4 2 4 3 3 4 4 6% 9% 56%	4071
	21st to end	Day	6% 5% 2 5% 4 4 5% 4 7% 7% 51%	4477
June	1st to 10th	Day	3 3 1 3 3 4 4 4 7% 8% 58%	2470
	11th to 20th	Day	4 3 1 4 3 2 3 3 5% 7% 64%	2470
	21st to end	Day	2 2 1 2 3 3 4 3 4 5% 71%	2470
July	1st to 10th	Day	1 1 1 2 2 2 2 2 4 5% 78%	4110
	11th to 20th	Day	2 2 1 3 4 5% 5% 5% 7% 10% 57%	4110
	21st to end	Day	2 2 1 3 3 4 4 3 6% 7% 66%	4454
August	1st to 10th	Day	2 2 1 4 3 3 4 4 6% 8% 63%	4092
	11th to 20th	Day	2 2 1 3 3 4 4 4 5% 7% 66%	4028
	21st to end	Day	2 2 1 3 2 2 3 4 5% 7% 69%	4461
September	1st to 10th	Day	3 3 1 2 2 3 3 4 5% 7% 68%	2149
	11th to 20th	Day	3 2 1 3 3 3 3 3 5% 7% 66%	2090
	21st to end	Day	5% 3 1 3 3 2 3 2 2 6% 70%	2090
October	1st to 10th	Day	7% 5% 2 5% 4 3 4 3 5% 6% 58%	1992
	11th to 20th	Day	7% 6% 2 3 2 2 3 2 4 7% 62%	1900
	21st to end	Day	6% 7% 2 4 2 3 4 3 5% 6% 58%	2090
November	1st to 10th	Day	8% 9% 2 5% 3 4 4 3 4 6% 52%	1714
	11th to 20th	Day	12% 7% 2 5% 4 3 4 3 5% 7% 48%	1710
	21st to end	Day	6% 11% 4 7% 4 3 3 3 5% 8% 46%	1611
December	1st to 10th	Day	9% 13% 4 8% 3 3 3 3 4 6% 44%	1520
	11th to 20th	Day	9% 12% 4 10% 5% 4 5% 4 6% 7% 34%	1958
	21st to end	Day	8% 13% 5% 9% 5% 4 4 4 6% 8% 35%	3146
January	1st to 10th	Night	7% 18% 7% 11% 4 4 3 3 4 5% 33%	4097
	11th to 20th	Night	13% 19% 6% 12% 4 4 3 2 4 5% 29%	4110
	21st to end	Night	9% 18% 4 7% 3 3 3 3 4 7% 37%	4521
February	1st to 10th	Night	9% 13% 4 9% 4 4 4 4 5% 6% 39%	2470
	11th to 20th	Night	9% 11% 4 8% 5% 3 3 3 4 6% 42%	2332
	21st to end	Night	7% 13% 5% 10% 3 3 4 4 6% 6% 40%	1884
March	1st to 10th	Night	6% 15% 8% 8% 4 4 5% 3 5% 6% 36%	3494
	11th to 20th	Night	5% 9% 2 5% 5% 4 5% 4 6% 7% 48%	3490
	21st to end	Night	8% 19% 4 9% 5% 5% 4 3 4 6% 34%	3828
April	1st to 10th	Night	10% 10% 2 6% 4 3 3 3 3 6% 50%	2069
	11th to 20th	Night	7% 8% 2 6% 4 5% 4 3 6% 7% 49%	1752
	21st to end	Night	9% 7% 2 6% 3 3 4 3 5% 6% 50%	1710
May	1st to 10th	Night	9% 10% 3 7% 5% 3 4 4 6% 8% 42%	2860
	11th to 20th	Night	5% 4 1 4 3 4 4 3 5% 8% 60%	2834
	21st to end	Night	6% 4 1 5% 3 3 4 4 6% 7% 56%	3110
June	1st to 10th	Night	4 3 2 3 3 4 5% 4 6% 7% 59%	1710
	11th to 20th	Night	4 3 1 3 2 3 3 3 4 6% 67%	1710
	21st to end	Night	2 2 1 3 3 3 2 3 6% 7% 68%	1710
July	1st to 10th	Night	1 2 1 3 2 3 4 3 4 4 73%	2860
	11th to 20th	Night	2 3 1 5% 5% 5% 7% 6% 8% 10% 47%	2860
	21st to end	Night	1 4 1 6% 4 5% 6% 4 5% 7% 58%	3109
August	1st to 10th	Night	3 2 1 4 4 4 5% 4 6% 9% 58%	2847
	11th to 20th	Night	2 3 1 5% 4 4 4 4 5% 6% 60%	2811
	21st to end	Night	1 1 1 3 3 2 3 3 4 6% 73%	3205
September	1st to 10th	Night	2 2 1 3 3 3 3 3 4 6% 71%	2027
	11th to 20th	Night	4 3 1 4 2 2 3 3 5% 7% 66%	2090
	21st to end	Night	6% 3 1 3 2 2 3 2 3 5% 71%	2090
October	1st to 10th	Night	6% 5% 2 4 3 3 3 2 5% 6% 62%	2186
	11th to 20th	Night	7% 6% 2 3 2 3 2 3 4 6% 62%	2280
	21st to end	Night	5% 7% 2 4 3 2 3 3 4 6% 60%	2508
November	1st to 10th	Night	7% 8% 2 5% 3 3 3 3 5% 7% 54%	2406
	11th to 20th	Night	9% 7% 2 4 3 3 3 3 5% 7% 52%	2470
	21st to end	Night	7% 12% 4 6% 3 4 3 2 4 6% 48%	2546
December	1st to 10th	Night	10% 12% 4 6% 3 3 2 2 4 6% 47%	2660
	11th to 20th	Night	11% 14% 4 7% 4 4 4 4 5% 8% 36%	3263
	21st to end	Night	7% 14% 6% 10% 5% 4 4 4 6% 6% 33%	4521

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	54% 7% 12% 16% 9%	2859
	11th to 20th	Day	58% 6% 15% 13% 7% 1	2860
	21st to end	Day	47% 8% 17% 17% 9% 2	3146
February	1st to 10th	Day	49% 6% 14% 18% 10% 2	1710
	11th to 20th	Day	48% 5% 12% 21% 13% 1	1743
	21st to end	Day	47% 5% 12% 23% 13% 1	1570
March	1st to 10th	Day	39% 9% 13% 23% 14% 3	3379
	11th to 20th	Day	35% 9% 13% 29% 13% 2	3490
	21st to end	Day	54% 9% 13% 14% 8% 1	3825
April	1st to 10th	Day	40% 6% 11% 20% 17% 6%	2109
	11th to 20th	Day	40% 5% 12% 19% 20% 4	2374
	21st to end	Day	35% 5% 10% 25% 22% 3	2470
May	1st to 10th	Day	37% 8% 11% 18% 21% 5%	4110
	11th to 20th	Day	22% 6% 10% 27% 31% 4	4074
	21st to end	Day	27% 7% 10% 23% 28% 5%	4477
June	1st to 10th	Day	21% 5% 8% 18% 34% 13%	2470
	11th to 20th	Day	19% 4 7% 14% 31% 25%	2470
	21st to end	Day	15% 3 5% 9% 28% 40%	2470
July	1st to 10th	Day	10% 3 4 7% 13% 63%	4046
	11th to 20th	Day	20% 5% 5% 11% 28% 31%	4041
	21st to end	Day	17% 5% 7% 12% 21% 39%	4314
August	1st to 10th	Day	18% 4 7% 20% 26% 24%	4078
	11th to 20th	Day	18% 4 7% 15% 29% 27%	4067
	21st to end	Day	15% 3 6% 13% 31% 32%	4460
September	1st to 10th	Day	16% 4 8% 13% 29% 31%	2149
	11th to 20th	Day	19% 4 7% 19% 26% 25%	2090
	21st to end	Day	18% 3 6% 18% 35% 20%	2090
October	1st to 10th	Day	28% 5% 7% 17% 32% 10%	1992
	11th to 20th	Day	25% 3 7% 25% 31% 8%	1900
	21st to end	Day	27% 4 12% 29% 24% 4	2090
November	1st to 10th	Day	34% 4 11% 25% 21% 5%	1714
	11th to 20th	Day	35% 6% 12% 26% 19% 2	1710
	21st to end	Day	37% 5% 13% 26% 16% 3	1611
December	1st to 10th	Day	41% 4 17% 24% 10% 3	1520
	11th to 20th	Day	45% 7% 13% 23% 11%	1956
	21st to end	Day	44% 8% 15% 13% 18% 1	3146
January	1st to 10th	Night	51% 7% 12% 18% 10%	4097
	11th to 20th	Night	57% 7% 13% 15% 6% 1	4110
	21st to end	Night	45% 10% 20% 17% 7% 2	4521
February	1st to 10th	Night	44% 7% 17% 22% 8% 2	2470
	11th to 20th	Night	43% 6% 11% 22% 16% 2	2333
	21st to end	Night	43% 5% 11% 24% 14% 3	1884
March	1st to 10th	Night	42% 9% 12% 23% 14% 1	3494
	11th to 20th	Night	31% 7% 12% 32% 15% 2	3490
	21st to end	Night	47% 8% 11% 18% 15% 2	3828
April	1st to 10th	Night	36% 4 12% 23% 18% 7%	2069
	11th to 20th	Night	33% 5% 12% 24% 22% 4	1752
	21st to end	Night	33% 6% 11% 27% 20% 3	1710
May	1st to 10th	Night	36% 6% 9% 21% 22% 5%	2860
	11th to 20th	Night	21% 6% 8% 27% 33% 5%	2835
	21st to end	Night	23% 5% 10% 30% 28% 4	3110
June	1st to 10th	Night	21% 6% 10% 21% 31% 12%	1710
	11th to 20th	Night	19% 3 7% 16% 30% 25%	1710
	21st to end	Night	16% 3 5% 9% 26% 41%	1710
July	1st to 10th	Night	14% 3 5% 6% 11% 61%	2815
	11th to 20th	Night	26% 7% 5% 11% 24% 26%	2806
	21st to end	Night	25% 5% 8% 11% 19% 32%	3011
August	1st to 10th	Night	21% 6% 8% 21% 21% 23%	2838
	11th to 20th	Night	22% 5% 8% 14% 24% 27%	2838
	21st to end	Night	13% 3 7% 11% 29% 35%	3205
September	1st to 10th	Night	16% 3 7% 15% 26% 33%	2027
	11th to 20th	Night	18% 4 7% 19% 26% 25%	2090
	21st to end	Night	18% 3 5% 16% 33% 25%	2090
October	1st to 10th	Night	24% 4 8% 21% 30% 14%	2186
	11th to 20th	Night	24% 3 7% 23% 33% 9%	2280
	21st to end	Night	24% 5% 9% 30% 25% 5%	2508
November	1st to 10th	Night	29% 5% 10% 27% 23% 6%	2406
	11th to 20th	Night	30% 5% 13% 30% 19% 3	2470
	21st to end	Night	38% 4 8% 25% 20% 4	2546
December	1st to 10th	Night	39% 5% 16% 27% 11% 3	2660
	11th to 20th	Night	44% 8% 14% 22% 12%	3264
	21st to end	Night	49% 8% 13% 14% 15% 1	4521

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	23% 7% 21% 30% 14% 4	270
	11th to 20th	Day	15% 11% 22% 34% 16% 3	270
	21st to end	Day	16% 5% 26% 31% 19% 3	297
February	1st to 10th	Day	18% 12% 26% 33% 10% 1	270
	11th to 20th	Day	14% 12% 30% 31% 12% 1	339
	21st to end	Day	10% 14% 36% 30% 9% 1	382
March	1st to 10th	Day	15% 18% 25% 29% 12% 1	460
	11th to 20th	Day	10% 12% 36% 29% 13% 1	460
	21st to end	Day	16% 19% 33% 25% 7%	506
April	1st to 10th	Day	14% 16% 25% 28% 14% 3	460
	11th to 20th	Day	14% 22% 28% 25% 10% 2	452
	21st to end	Day	13% 19% 26% 27% 14% 2	460
May	1st to 10th	Day	11% 16% 33% 26% 12% 2	463
	11th to 20th	Day	8% 11% 30% 30% 18% 4	488
	21st to end	Day	8% 11% 25% 29% 22% 5%	529
June	1st to 10th	Day	4 12% 23% 38% 19% 5%	490
	11th to 20th	Day	6% 14% 30% 33% 14% 3	490
	21st to end	Day	3 7% 31% 39% 16% 4	490
July	1st to 10th	Day	2 5% 24% 38% 25% 6%	486
	11th to 20th	Day	3 2 24% 41% 24% 5%	484
	21st to end	Day	2 1 15% 44% 31% 7%	531
August	1st to 10th	Day	6% 4 18% 41% 26% 5%	487
	11th to 20th	Day	3 3 23% 38% 27% 7%	477
	21st to end	Day	2 4 23% 35% 28% 7%	539
September	1st to 10th	Day	4 4 20% 33% 29% 10%	490
	11th to 20th	Day	5% 10% 24% 31% 23% 7%	490
	21st to end	Day	6% 9% 19% 29% 31% 7%	490
October	1st to 10th	Day	5% 10% 23% 29% 25% 9%	392
	11th to 20th	Day	7% 11% 22% 25% 26% 9%	300
	21st to end	Day	9% 8% 26% 33% 22% 2	330
November	1st to 10th	Day	15% 13% 17% 27% 20% 7%	276
	11th to 20th	Day	11% 8% 19% 34% 21% 7%	270
	21st to end	Day	11% 6% 21% 32% 26% 5%	270
December	1st to 10th	Day	12% 11% 19% 35% 15% 7%	270
	11th to 20th	Day	12% 9% 21% 39% 17% 2	270
	21st to end	Day	18% 9% 21% 35% 13% 3	297
January	1st to 10th	Night	18% 4 15% 41% 18% 5%	760
	11th to 20th	Night	16% 5% 17% 37% 23% 3	760
	21st to end	Night	17% 4 15% 42% 19% 3	836
February	1st to 10th	Night	14% 5% 23% 43% 12% 3	760
	11th to 20th	Night	14% 4 23% 42% 16% 1	744
	21st to end	Night	13% 5% 24% 43% 14% 1	628
March	1st to 10th	Night	16% 8% 19% 41% 14% 2	760
	11th to 20th	Night	9% 5% 19% 44% 21% 1	760
	21st to end	Night	13% 8% 23% 40% 13% 2	836
April	1st to 10th	Night	14% 8% 21% 40% 15% 1	739
	11th to 20th	Night	11% 9% 24% 42% 15%	563
	21st to end	Night	11% 8% 21% 40% 19% 1	570
May	1st to 10th	Night	10% 6% 25% 39% 18% 2	570
	11th to 20th	Night	8% 4 17% 41% 28% 2	561
	21st to end	Night	8% 7% 16% 41% 25% 3	617
June	1st to 10th	Night	5% 6% 18% 40% 29% 2	570
	11th to 20th	Night	6% 5% 24% 41% 22% 1	570
	21st to end	Night	2 3 19% 42% 32% 2	570
July	1st to 10th	Night	3 1 15% 36% 42% 3	555
	11th to 20th	Night	4 1 9% 46% 37% 3	552
	21st to end	Night	3 2 8% 37% 48% 3	624
August	1st to 10th	Night	4 1 11% 46% 36% 2	567
	11th to 20th	Night	3 3 13% 44% 36% 2	564
	21st to end	Night	4 2 13% 41% 39% 2	627
September	1st to 10th	Night	3 1 12% 41% 37% 5%	697
	11th to 20th	Night	5% 3 15% 37% 34% 6%	760
	21st to end	Night	7% 3 15% 34% 33% 8%	760
October	1st to 10th	Night	7% 4 18% 42% 25% 3	760
	11th to 20th	Night	9% 3 19% 40% 25% 4	760
	21st to end	Night	9% 4 18% 39% 26% 4	836
November	1st to 10th	Night	10% 5% 17% 37% 26% 4	748
	11th to 20th	Night	13% 4 17% 41% 21% 4	760
	21st to end	Night	12% 5% 18% 38% 22% 5%	836
December	1st to 10th	Night	17% 4 17% 43% 18% 2	950
	11th to 20th	Night	20% 5% 18% 42% 15% 1	942
	21st to end	Night	21% 6% 17% 42% 13% 2	836

Page generated at 2024-10-31 01:39:23. Version ac07

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