Pendleton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pendleton clear sky chart from 2005-11-06 to 2024-11-05.

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	9% 7% 2 6% 4 4 4 3 5% 6% 49%	105280
	Night	12% 9% 3 7% 4 4 4 3 5% 6% 43%	102421
Transparency	Day	35% 6% 12% 21% 17% 9%	105026
	Night	40% 7% 12% 20% 14% 7%	102264
Seeing	Day	13% 10% 23% 29% 20% 5%	14416
	Night	17% 7% 20% 33% 19% 4	23507

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	19% 16% 5% 11% 7% 5% 5% 4 6% 6% 16%	2539
	11th to 20th	Day	24% 17% 4 9% 6% 4 5% 4 6% 5% 16%	2540
	21st to end	Day	22% 15% 5% 11% 6% 6% 4 3 5% 7% 17%	2794
February	1st to 10th	Day	19% 15% 4 9% 4 4 4 4 4 7% 26%	1650
	11th to 20th	Day	16% 13% 5% 8% 5% 5% 5% 4 5% 6% 30%	1759
	21st to end	Day	14% 12% 5% 9% 6% 5% 5% 5% 7% 6% 26%	1570
March	1st to 10th	Day	13% 10% 3 8% 5% 5% 5% 4 7% 8% 31%	3138
	11th to 20th	Day	8% 7% 3 5% 4 4 4 4 5% 6% 50%	3270
	21st to end	Day	14% 10% 4 11% 7% 7% 6% 4 6% 7% 24%	4162
April	1st to 10th	Day	11% 10% 3 8% 5% 5% 5% 5% 7% 6% 34%	2280
	11th to 20th	Day	9% 8% 2 7% 5% 5% 4 4 6% 8% 41%	2249
	21st to end	Day	9% 8% 3 7% 4 4 4 5% 6% 6% 44%	2437
May	1st to 10th	Day	11% 6% 2 5% 3 4 4 3 6% 8% 48%	4349
	11th to 20th	Day	6% 3 1 4 3 3 3 3 5% 6% 63%	4377
	21st to end	Day	8% 7% 2 5% 4 4 5% 4 7% 8% 44%	4813
June	1st to 10th	Day	12% 6% 2 5% 4 4 4 4 6% 8% 44%	2660
	11th to 20th	Day	9% 5% 2 4 4 3 4 4 5% 7% 52%	2660
	21st to end	Day	4 3 1 3 2 2 3 3 5% 6% 67%	2660
July	1st to 10th	Day	1 1 2 2 1 2 1 3 3 83%	4420
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 4 81%	4420
	21st to end	Day	1 1 1 2 1 2 2 2 3 5% 80%	4790
August	1st to 10th	Day	2 3 1 3 2 2 3 2 4 6% 71%	4400
	11th to 20th	Day	1 1 1 3 2 2 3 3 4 6% 75%	4010
	21st to end	Day	3 3 2 3 2 3 3 2 4 4 72%	4180
September	1st to 10th	Day	3 2 1 2 2 2 2 2 5% 6% 73%	2280
	11th to 20th	Day	6% 4 2 4 4 3 4 4 5% 7% 58%	2218
	21st to end	Day	7% 5% 3 5% 5% 4 4 3 3 5% 57%	2090
October	1st to 10th	Day	7% 4 2 4 3 2 4 2 4 5% 63%	3257
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 7% 10% 46%	3112
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 5% 7% 37%	3101
November	1st to 10th	Day	20% 8% 3 6% 5% 5% 5% 5% 6% 6% 30%	1710
	11th to 20th	Day	19% 12% 4 8% 6% 6% 5% 4 5% 7% 22%	1623
	21st to end	Day	17% 13% 4 8% 6% 6% 5% 4 6% 7% 25%	1520
December	1st to 10th	Day	18% 12% 4 9% 5% 6% 4 4 7% 6% 24%	1520
	11th to 20th	Day	19% 13% 6% 19% 9% 5% 5% 4 4 3 13%	1928
	21st to end	Day	18% 12% 4 16% 8% 6% 5% 4 5% 6% 16%	2794
January	1st to 10th	Night	23% 17% 6% 12% 6% 5% 5% 3 4 4 13%	4406
	11th to 20th	Night	24% 17% 5% 10% 4 4 4 4 4 6% 17%	4420
	21st to end	Night	19% 12% 5% 11% 6% 6% 5% 4 6% 6% 18%	4862
February	1st to 10th	Night	19% 15% 3 8% 5% 4 4 3 4 5% 28%	2527
	11th to 20th	Night	17% 13% 4 9% 5% 4 4 3 4 5% 31%	2306
	21st to end	Night	14% 16% 4 8% 6% 5% 4 4 5% 7% 28%	1884
March	1st to 10th	Night	11% 10% 4 7% 6% 5% 5% 4 6% 8% 35%	3736
	11th to 20th	Night	9% 9% 2 5% 4 3 3 3 5% 6% 50%	3707
	21st to end	Night	12% 12% 4 9% 7% 6% 6% 5% 7% 7% 24%	3490
April	1st to 10th	Night	14% 10% 3 6% 6% 4 4 4 6% 7% 35%	1900
	11th to 20th	Night	13% 9% 3 7% 5% 4 3 3 5% 6% 43%	1879
	21st to end	Night	10% 8% 3 7% 4 5% 5% 4 7% 7% 42%	1743
May	1st to 10th	Night	12% 6% 2 6% 3 5% 5% 4 5% 7% 45%	2609
	11th to 20th	Night	7% 4 2 4 3 3 3 4 4 7% 59%	2516
	21st to end	Night	10% 6% 2 6% 4 3 4 4 6% 7% 47%	2762
June	1st to 10th	Night	10% 6% 2 6% 4 3 4 6% 7% 8% 44%	1520
	11th to 20th	Night	9% 6% 2 7% 5% 4 4 4 5% 6% 49%	1520
	21st to end	Night	4 3 2 4 3 3 3 4 5% 6% 64%	1520
July	1st to 10th	Night	1 1 1 2 2 2 2 2 3 4 82%	2540
	11th to 20th	Night	1 1 1 1 1 2 2 3 5% 83%	2540
	21st to end	Night	2 1 2 1 2 2 2 3 4 80%	2761
August	1st to 10th	Night	3 2 2 2 2 3 2 5% 7% 70%	2529
	11th to 20th	Night	2 2 1 3 2 2 2 3 5% 6% 72%	2825
	21st to end	Night	2 2 1 4 2 2 2 2 3 6% 73%	3498
September	1st to 10th	Night	4 2 1 3 2 2 2 2 3 5% 73%	1900
	11th to 20th	Night	6% 4 1 4 3 4 3 3 5% 6% 60%	1961
	21st to end	Night	8% 4 1 4 3 4 4 3 4 7% 57%	2090
October	1st to 10th	Night	6% 5% 2 4 2 3 2 2 3 5% 65%	3707
	11th to 20th	Night	8% 4 2 5% 4 5% 4 4 6% 8% 50%	3824
	21st to end	Night	12% 8% 3 7% 4 5% 5% 3 5% 8% 41%	4457
November	1st to 10th	Night	19% 10% 3 8% 5% 4 4 3 4 6% 34%	2469
	11th to 20th	Night	21% 12% 4 8% 5% 5% 5% 3 6% 6% 26%	2555
	21st to end	Night	16% 12% 3 7% 6% 5% 5% 4 5% 6% 30%	2660
December	1st to 10th	Night	18% 13% 4 10% 7% 5% 5% 4 5% 6% 24%	2660
	11th to 20th	Night	20% 15% 6% 14% 8% 5% 5% 3 5% 5% 14%	3276
	21st to end	Night	18% 12% 4 18% 7% 5% 5% 4 4 5% 19%	4862

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	64% 14% 13% 8% 1	2539
	11th to 20th	Day	65% 10% 13% 10% 2	2540
	21st to end	Day	65% 11% 11% 10% 3	2794
February	1st to 10th	Day	59% 8% 16% 13% 4	1650
	11th to 20th	Day	55% 7% 16% 16% 7%	1768
	21st to end	Day	56% 8% 14% 15% 7% 1	1570
March	1st to 10th	Day	47% 6% 12% 24% 10%	3138
	11th to 20th	Day	34% 6% 16% 32% 12%	3270
	21st to end	Day	54% 10% 15% 17% 4	4162
April	1st to 10th	Day	47% 6% 17% 19% 10%	2280
	11th to 20th	Day	39% 6% 16% 22% 14% 3	2252
	21st to end	Day	39% 7% 15% 23% 15% 2	2437
May	1st to 10th	Day	33% 5% 12% 30% 18% 2	4349
	11th to 20th	Day	23% 4 9% 29% 26% 8%	4380
	21st to end	Day	34% 7% 19% 27% 11% 2	4814
June	1st to 10th	Day	38% 6% 14% 25% 15% 3	2660
	11th to 20th	Day	30% 5% 12% 29% 20% 4	2660
	21st to end	Day	18% 4 10% 30% 28% 10%	2660
July	1st to 10th	Day	9% 2 5% 13% 25% 46%	4351
	11th to 20th	Day	10% 2 5% 8% 24% 52%	4345
	21st to end	Day	10% 2 5% 17% 36% 31%	4639
August	1st to 10th	Day	16% 2 5% 14% 36% 27%	4384
	11th to 20th	Day	12% 3 6% 37% 32% 11%	4052
	21st to end	Day	18% 3 8% 28% 32% 12%	4179
September	1st to 10th	Day	14% 3 10% 26% 30% 17%	2280
	11th to 20th	Day	25% 4 12% 23% 25% 11%	2218
	21st to end	Day	30% 4 13% 28% 20% 5%	2090
October	1st to 10th	Day	25% 3 10% 31% 26% 5%	3257
	11th to 20th	Day	31% 6% 19% 28% 15% 1	3112
	21st to end	Day	45% 4 13% 28% 10% 1	3101
November	1st to 10th	Day	51% 7% 15% 21% 6% 1	1710
	11th to 20th	Day	60% 8% 15% 15% 2	1623
	21st to end	Day	55% 10% 16% 15% 4	1520
December	1st to 10th	Day	57% 10% 14% 15% 4 1	1520
	11th to 20th	Day	63% 18% 10% 8% 1	1928
	21st to end	Day	59% 16% 13% 10% 2	2794
January	1st to 10th	Night	69% 12% 11% 8% 1	4406
	11th to 20th	Night	65% 8% 15% 9% 3	4420
	21st to end	Night	59% 13% 15% 10% 2	4862
February	1st to 10th	Night	58% 6% 15% 16% 4	2527
	11th to 20th	Night	55% 6% 16% 18% 6%	2308
	21st to end	Night	55% 7% 13% 18% 6% 1	1884
March	1st to 10th	Night	45% 6% 9% 24% 14% 1	3736
	11th to 20th	Night	33% 5% 12% 38% 11%	3707
	21st to end	Night	53% 10% 17% 15% 4	3490
April	1st to 10th	Night	47% 7% 14% 22% 9%	1900
	11th to 20th	Night	42% 6% 15% 22% 12% 3	1879
	21st to end	Night	39% 7% 15% 20% 16% 2	1743
May	1st to 10th	Night	36% 5% 15% 23% 20% 2	2609
	11th to 20th	Night	24% 5% 9% 36% 24% 3	2516
	21st to end	Night	32% 9% 23% 27% 8% 1	2762
June	1st to 10th	Night	36% 7% 12% 25% 15% 4	1520
	11th to 20th	Night	35% 5% 12% 30% 15% 4	1520
	21st to end	Night	21% 4 10% 30% 23% 11%	1520
July	1st to 10th	Night	8% 2 6% 14% 26% 44%	2500
	11th to 20th	Night	7% 2 6% 11% 21% 54%	2492
	21st to end	Night	9% 2 4 15% 32% 37%	2674
August	1st to 10th	Night	15% 2 5% 14% 35% 29%	2521
	11th to 20th	Night	14% 3 6% 36% 30% 12%	2849
	21st to end	Night	16% 3 8% 29% 31% 14%	3498
September	1st to 10th	Night	16% 2 9% 23% 31% 18%	1900
	11th to 20th	Night	24% 5% 10% 25% 22% 14%	1961
	21st to end	Night	27% 5% 12% 27% 23% 7%	2090
October	1st to 10th	Night	24% 3 10% 28% 32% 3	3707
	11th to 20th	Night	32% 5% 17% 24% 20% 2	3824
	21st to end	Night	42% 5% 11% 29% 13% 1	4457
November	1st to 10th	Night	52% 6% 11% 23% 7% 1	2469
	11th to 20th	Night	57% 7% 14% 18% 4	2555
	21st to end	Night	50% 10% 15% 19% 6%	2660
December	1st to 10th	Night	60% 9% 14% 14% 3	2660
	11th to 20th	Night	64% 13% 11% 10% 2	3276
	21st to end	Night	55% 17% 11% 12% 4	4862

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	32% 12% 24% 16% 12% 5%	180
	11th to 20th	Day	27% 11% 21% 27% 9% 6%	180
	21st to end	Day	25% 9% 19% 27% 16% 3	198
February	1st to 10th	Day	30% 11% 24% 25% 10% 1	310
	11th to 20th	Day	26% 13% 22% 25% 12% 2	410
	21st to end	Day	19% 15% 26% 27% 12% 1	382
March	1st to 10th	Day	21% 14% 27% 26% 12% 1	460
	11th to 20th	Day	15% 14% 26% 24% 17% 4	460
	21st to end	Day	17% 13% 31% 24% 13% 2	506
April	1st to 10th	Day	19% 16% 27% 21% 13% 3	460
	11th to 20th	Day	13% 16% 30% 22% 15% 4	452
	21st to end	Day	11% 17% 24% 26% 19% 3	460
May	1st to 10th	Day	11% 11% 27% 30% 17% 4	463
	11th to 20th	Day	16% 9% 22% 30% 16% 7%	488
	21st to end	Day	12% 8% 22% 27% 25% 7%	529
June	1st to 10th	Day	13% 10% 20% 29% 21% 8%	490
	11th to 20th	Day	11% 14% 31% 25% 17% 2	490
	21st to end	Day	5% 8% 24% 31% 24% 8%	490
July	1st to 10th	Day	2 5% 21% 43% 26% 4	486
	11th to 20th	Day	2 7% 23% 39% 25% 4	484
	21st to end	Day	2 5% 20% 39% 26% 8%	531
August	1st to 10th	Day	3 4 20% 39% 26% 9%	487
	11th to 20th	Day	2 3 19% 31% 34% 10%	477
	21st to end	Day	5% 6% 21% 36% 24% 8%	539
September	1st to 10th	Day	3 6% 20% 33% 29% 10%	490
	11th to 20th	Day	7% 7% 22% 30% 28% 7%	490
	21st to end	Day	9% 9% 19% 29% 27% 6%	490
October	1st to 10th	Day	13% 7% 21% 29% 25% 5%	490
	11th to 20th	Day	11% 11% 21% 29% 20% 8%	466
	21st to end	Day	22% 9% 24% 26% 15% 5%	330
November	1st to 10th	Day	24% 9% 27% 23% 16% 1	282
	11th to 20th	Day	21% 12% 21% 26% 15% 5%	228
	21st to end	Day	18% 9% 21% 31% 17% 6%	180
December	1st to 10th	Day	20% 9% 24% 21% 17% 9%	180
	11th to 20th	Day	28% 11% 28% 22% 11% 2	180
	21st to end	Day	23% 7% 27% 29% 10% 4	198
January	1st to 10th	Night	30% 11% 18% 23% 15% 3	760
	11th to 20th	Night	28% 10% 18% 24% 17% 3	760
	21st to end	Night	23% 7% 19% 29% 17% 4	836
February	1st to 10th	Night	27% 9% 21% 26% 14% 2	760
	11th to 20th	Night	23% 9% 19% 31% 15% 2	744
	21st to end	Night	21% 14% 24% 29% 10% 2	628
March	1st to 10th	Night	19% 12% 23% 30% 14% 3	760
	11th to 20th	Night	17% 8% 22% 32% 18% 3	760
	21st to end	Night	20% 11% 26% 29% 13% 1	836
April	1st to 10th	Night	19% 10% 20% 34% 14% 3	760
	11th to 20th	Night	17% 10% 26% 26% 16% 4	751
	21st to end	Night	13% 10% 27% 31% 17% 2	603
May	1st to 10th	Night	10% 8% 27% 36% 16% 4	423
	11th to 20th	Night	13% 6% 17% 36% 23% 6%	374
	21st to end	Night	10% 8% 20% 39% 19% 5%	411
June	1st to 10th	Night	12% 6% 27% 33% 19% 3	380
	11th to 20th	Night	13% 10% 31% 32% 13% 1	380
	21st to end	Night	6% 4 27% 41% 19% 3	380
July	1st to 10th	Night	2 4 23% 45% 23% 4	370
	11th to 20th	Night	2 2 27% 48% 17% 3	368
	21st to end	Night	1 2 19% 49% 25% 3	416
August	1st to 10th	Night	3 2 17% 47% 28% 3	378
	11th to 20th	Night	3 1 13% 39% 33% 11%	561
	21st to end	Night	4 3 17% 38% 30% 7%	836
September	1st to 10th	Night	4 3 14% 42% 31% 7%	760
	11th to 20th	Night	6% 3 15% 34% 30% 11%	760
	21st to end	Night	9% 4 18% 33% 27% 9%	760
October	1st to 10th	Night	13% 3 15% 40% 25% 4	760
	11th to 20th	Night	12% 6% 19% 32% 25% 6%	760
	21st to end	Night	16% 8% 22% 31% 18% 6%	836
November	1st to 10th	Night	22% 8% 21% 34% 15% 1	760
	11th to 20th	Night	24% 9% 21% 28% 14% 4	760
	21st to end	Night	19% 9% 17% 31% 18% 5%	760
December	1st to 10th	Night	26% 7% 17% 30% 16% 4	760
	11th to 20th	Night	28% 8% 19% 31% 12% 2	760
	21st to end	Night	31% 10% 21% 26% 12% 1	836

Page generated at 2024-11-02 23:11:06. Version ac07

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