Jasper
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper clear sky chart from 2005-11-06 to 2024-11-02.

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	7% 11% 4 12% 7% 7% 6% 5% 7% 7% 26%	102016
	Night	4 10% 4 11% 7% 7% 6% 5% 8% 9% 28%	97012
Transparency	Day	56% 8% 13% 15% 7% 1	101757
	Night	52% 9% 16% 16% 6% 1	96917
Seeing	Day	19% 14% 29% 24% 11% 3	16123
	Night	12% 11% 36% 30% 11% 1	24332

By Month

Percentage Cloud Cover NW (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	1 6% 8% 16% 11% 11% 8% 6% 8% 8% 16%	1899
	11th to 20th	Day	1 7% 5% 13% 7% 6% 7% 6% 9% 7% 32%	2183
	21st to end	Day	2 17% 5% 14% 9% 7% 8% 6% 8% 7% 18%	2794
February	1st to 10th	Day	2 10% 6% 15% 9% 7% 7% 5% 8% 8% 22%	1520
	11th to 20th	Day	1 10% 6% 16% 9% 7% 7% 6% 8% 8% 22%	1564
	21st to end	Day	1 8% 5% 16% 12% 8% 6% 6% 9% 6% 23%	1553
March	1st to 10th	Day	5% 3 14% 11% 11% 10% 7% 8% 10% 21%	3138
	11th to 20th	Day	2 11% 5% 12% 8% 6% 6% 5% 8% 8% 29%	3252
	21st to end	Day	1 14% 7% 19% 10% 6% 6% 5% 6% 8% 18%	4165
April	1st to 10th	Day	3 15% 7% 18% 9% 10% 8% 5% 6% 6% 14%	2280
	11th to 20th	Day	3 15% 7% 17% 9% 7% 6% 5% 5% 7% 19%	2377
	21st to end	Day	7% 17% 6% 14% 8% 6% 6% 4 7% 7% 20%	2617
May	1st to 10th	Day	8% 20% 6% 12% 6% 6% 4 4 5% 6% 22%	4420
	11th to 20th	Day	10% 15% 5% 11% 7% 7% 6% 5% 7% 7% 21%	4584
	21st to end	Day	15% 21% 6% 14% 8% 6% 6% 4 5% 4 13%	5188
June	1st to 10th	Day	18% 13% 4 12% 7% 6% 5% 5% 7% 6% 18%	3040
	11th to 20th	Day	19% 17% 5% 12% 7% 6% 6% 4 5% 4 13%	3040
	21st to end	Day	12% 12% 5% 12% 8% 6% 6% 5% 6% 6% 21%	3040
July	1st to 10th	Day	10% 8% 2 7% 5% 5% 5% 4 5% 6% 43%	5060
	11th to 20th	Day	7% 6% 2 6% 5% 5% 5% 4 6% 7% 46%	5041
	21st to end	Day	9% 7% 3 8% 6% 7% 7% 6% 8% 8% 31%	4827
August	1st to 10th	Day	11% 7% 3 7% 5% 6% 5% 4 7% 8% 37%	4401
	11th to 20th	Day	11% 8% 3 8% 6% 6% 7% 5% 8% 9% 32%	4330
	21st to end	Day	12% 9% 3 7% 5% 6% 7% 5% 7% 9% 29%	4467
September	1st to 10th	Day	11% 10% 4 10% 6% 6% 5% 4 4 6% 34%	2280
	11th to 20th	Day	10% 10% 3 9% 5% 6% 6% 5% 7% 6% 34%	2218
	21st to end	Day	9% 12% 4 10% 7% 7% 6% 4 7% 6% 29%	2090
October	1st to 10th	Day	7% 14% 4 12% 6% 6% 5% 4 7% 8% 27%	1933
	11th to 20th	Day	4 12% 4 10% 7% 7% 7% 5% 7% 9% 27%	1750
	21st to end	Day	3 12% 5% 12% 7% 6% 7% 6% 7% 8% 26%	1881
November	1st to 10th	Day	3 12% 5% 14% 9% 8% 6% 5% 7% 8% 22%	1557
	11th to 20th	Day	2 8% 5% 11% 6% 7% 7% 6% 8% 12% 29%	1330
	21st to end	Day	1 12% 5% 12% 8% 7% 8% 5% 8% 10% 26%	1330
December	1st to 10th	Day	2 10% 4 13% 9% 7% 7% 7% 8% 8% 25%	1330
	11th to 20th	Day	1 10% 5% 12% 8% 9% 8% 6% 7% 10% 24%	1447
	21st to end	Day	9% 4 10% 7% 6% 8% 5% 9% 11% 32%	2090
January	1st to 10th	Night	1 8% 6% 17% 12% 8% 7% 5% 8% 9% 19%	5046
	11th to 20th	Night	1 7% 4 12% 7% 7% 7% 7% 9% 10% 28%	4741
	21st to end	Night	2 12% 5% 15% 9% 8% 7% 6% 7% 9% 19%	4862
February	1st to 10th	Night	3 10% 5% 13% 11% 7% 7% 7% 8% 9% 20%	2660
	11th to 20th	Night	1 9% 4 12% 8% 8% 8% 7% 7% 10% 25%	2499
	21st to end	Night	1 10% 5% 12% 9% 7% 7% 6% 8% 10% 24%	1900
March	1st to 10th	Night	5% 4 13% 12% 10% 8% 7% 9% 9% 22%	3736
	11th to 20th	Night	3 8% 5% 9% 7% 6% 6% 5% 11% 11% 29%	3725
	21st to end	Night	2 14% 7% 19% 8% 6% 5% 4 6% 10% 19%	3488
April	1st to 10th	Night	2 12% 6% 13% 9% 9% 7% 6% 8% 9% 21%	1900
	11th to 20th	Night	3 11% 5% 13% 8% 6% 6% 4 7% 9% 28%	1753
	21st to end	Night	5% 12% 5% 11% 6% 5% 7% 5% 7% 8% 28%	1561
May	1st to 10th	Night	5% 16% 5% 11% 6% 6% 6% 5% 6% 8% 25%	2540
	11th to 20th	Night	8% 12% 4 11% 7% 6% 6% 5% 6% 7% 28%	2309
	21st to end	Night	11% 16% 6% 12% 7% 7% 6% 5% 5% 7% 19%	2384
June	1st to 10th	Night	13% 11% 4 9% 6% 6% 6% 5% 6% 5% 29%	1140
	11th to 20th	Night	17% 12% 5% 9% 8% 6% 6% 5% 7% 7% 19%	1140
	21st to end	Night	9% 6% 2 9% 7% 6% 7% 5% 7% 9% 32%	1140
July	1st to 10th	Night	9% 6% 2 5% 3 4 5% 4 5% 7% 51%	1900
	11th to 20th	Night	6% 4 2 5% 3 4 5% 4 7% 8% 52%	1918
	21st to end	Night	8% 6% 3 7% 5% 4 5% 5% 7% 9% 40%	2722
August	1st to 10th	Night	9% 9% 3 8% 5% 4 5% 4 8% 9% 36%	2529
	11th to 20th	Night	12% 9% 3 6% 4 4 6% 5% 8% 9% 35%	2497
	21st to end	Night	12% 8% 2 7% 5% 5% 6% 5% 7% 8% 35%	3200
September	1st to 10th	Night	11% 9% 2 7% 5% 5% 5% 5% 5% 6% 39%	1900
	11th to 20th	Night	9% 11% 3 10% 5% 5% 4 5% 6% 7% 36%	1961
	21st to end	Night	8% 9% 4 8% 5% 5% 6% 5% 8% 9% 33%	2090
October	1st to 10th	Night	6% 13% 5% 11% 6% 6% 5% 4 7% 8% 29%	2246
	11th to 20th	Night	5% 12% 3 8% 7% 5% 7% 6% 8% 10% 29%	2429
	21st to end	Night	3 11% 4 12% 7% 6% 6% 6% 9% 9% 27%	2717
November	1st to 10th	Night	3 12% 5% 12% 9% 8% 6% 5% 8% 9% 22%	2539
	11th to 20th	Night	1 10% 5% 10% 7% 8% 7% 6% 8% 11% 28%	2834
	21st to end	Night	1 10% 5% 10% 10% 7% 7% 5% 9% 11% 25%	2850
December	1st to 10th	Night	3 8% 5% 12% 9% 7% 6% 5% 8% 10% 28%	2850
	11th to 20th	Night	1 9% 5% 14% 9% 9% 8% 6% 8% 9% 22%	3740
	21st to end	Night	1 9% 5% 10% 7% 6% 7% 6% 8% 10% 31%	5566

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	61% 11% 16% 10% 3 1	1899
	11th to 20th	Day	50% 10% 10% 12% 15% 3	2204
	21st to end	Day	59% 13% 15% 9% 4	2794
February	1st to 10th	Day	59% 7% 12% 11% 9% 2	1520
	11th to 20th	Day	60% 7% 10% 16% 6%	1572
	21st to end	Day	58% 6% 13% 14% 7% 2	1553
March	1st to 10th	Day	53% 11% 14% 14% 8%	3138
	11th to 20th	Day	52% 8% 16% 21% 4	3252
	21st to end	Day	62% 8% 12% 11% 7%	4165
April	1st to 10th	Day	71% 7% 11% 10% 1	2280
	11th to 20th	Day	65% 7% 12% 14% 2	2377
	21st to end	Day	64% 8% 13% 12% 2	2617
May	1st to 10th	Day	62% 6% 13% 14% 5%	4420
	11th to 20th	Day	60% 6% 14% 14% 6%	4588
	21st to end	Day	73% 8% 9% 7% 3	5189
June	1st to 10th	Day	65% 7% 11% 11% 5% 1	3040
	11th to 20th	Day	72% 7% 10% 8% 3	3040
	21st to end	Day	62% 8% 12% 13% 5% 1	3040
July	1st to 10th	Day	43% 7% 8% 20% 15% 7%	4981
	11th to 20th	Day	37% 7% 11% 24% 19% 3	4954
	21st to end	Day	50% 9% 11% 15% 11% 3	4674
August	1st to 10th	Day	42% 8% 13% 27% 10%	4384
	11th to 20th	Day	46% 9% 17% 21% 6% 1	4372
	21st to end	Day	52% 9% 13% 22% 5%	4466
September	1st to 10th	Day	52% 6% 14% 21% 5% 2	2280
	11th to 20th	Day	49% 7% 16% 19% 8% 1	2218
	21st to end	Day	56% 8% 13% 14% 7% 1	2090
October	1st to 10th	Day	54% 7% 17% 17% 4	1933
	11th to 20th	Day	54% 11% 16% 17% 3	1750
	21st to end	Day	57% 7% 16% 15% 5%	1881
November	1st to 10th	Day	59% 10% 14% 13% 4 1	1557
	11th to 20th	Day	49% 10% 23% 13% 5% 1	1330
	21st to end	Day	54% 10% 18% 10% 5% 3	1330
December	1st to 10th	Day	58% 9% 12% 15% 6% 1	1330
	11th to 20th	Day	55% 10% 15% 12% 6% 1	1449
	21st to end	Day	42% 10% 22% 15% 10%	2090
January	1st to 10th	Night	60% 8% 16% 11% 4 1	5046
	11th to 20th	Night	49% 9% 10% 12% 18% 2	4782
	21st to end	Night	61% 12% 12% 11% 3	4862
February	1st to 10th	Night	61% 8% 11% 11% 8% 1	2660
	11th to 20th	Night	55% 8% 16% 15% 6% 1	2501
	21st to end	Night	54% 6% 12% 20% 8% 1	1900
March	1st to 10th	Night	52% 13% 12% 16% 6% 1	3736
	11th to 20th	Night	45% 8% 21% 22% 4	3726
	21st to end	Night	59% 8% 14% 14% 5%	3488
April	1st to 10th	Night	60% 9% 15% 14% 2	1900
	11th to 20th	Night	52% 8% 16% 18% 5%	1753
	21st to end	Night	53% 9% 14% 18% 5%	1561
May	1st to 10th	Night	56% 8% 18% 16% 2	2540
	11th to 20th	Night	54% 9% 14% 15% 8%	2309
	21st to end	Night	64% 10% 12% 12% 3	2384
June	1st to 10th	Night	56% 6% 15% 16% 6% 1	1140
	11th to 20th	Night	62% 8% 16% 11% 4	1140
	21st to end	Night	47% 10% 19% 18% 6% 1	1140
July	1st to 10th	Night	34% 7% 13% 23% 21% 2	1870
	11th to 20th	Night	31% 7% 14% 28% 20% 1	1882
	21st to end	Night	41% 8% 16% 21% 9% 5%	2636
August	1st to 10th	Night	42% 9% 18% 28% 3	2521
	11th to 20th	Night	43% 10% 22% 20% 5%	2521
	21st to end	Night	47% 8% 23% 18% 4	3200
September	1st to 10th	Night	44% 7% 18% 23% 7% 1	1900
	11th to 20th	Night	47% 6% 19% 19% 7% 1	1961
	21st to end	Night	45% 11% 19% 19% 6% 1	2090
October	1st to 10th	Night	54% 8% 16% 18% 4	2246
	11th to 20th	Night	51% 10% 17% 19% 3	2429
	21st to end	Night	54% 9% 18% 13% 5%	2717
November	1st to 10th	Night	60% 8% 16% 13% 3	2539
	11th to 20th	Night	51% 12% 19% 12% 6%	2834
	21st to end	Night	54% 11% 16% 12% 5% 2	2850
December	1st to 10th	Night	53% 8% 16% 16% 7% 1	2850
	11th to 20th	Night	57% 12% 14% 12% 4	3737
	21st to end	Night	45% 9% 20% 19% 5% 1	5566

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	9% 9% 21% 41% 16% 3	180
	11th to 20th	Day	11% 7% 29% 37% 12% 4	180
	21st to end	Day	16% 8% 33% 29% 11% 4	198
February	1st to 10th	Day	17% 13% 36% 21% 11% 3	180
	11th to 20th	Day	15% 14% 29% 25% 13% 5%	264
	21st to end	Day	12% 17% 39% 19% 11% 2	375
March	1st to 10th	Day	15% 21% 31% 19% 11% 3	460
	11th to 20th	Day	14% 19% 35% 19% 9% 3	460
	21st to end	Day	16% 20% 29% 20% 9% 5%	506
April	1st to 10th	Day	20% 20% 31% 21% 7% 1	460
	11th to 20th	Day	17% 17% 29% 23% 10% 5%	452
	21st to end	Day	20% 18% 26% 22% 10% 3	460
May	1st to 10th	Day	22% 15% 30% 22% 8% 2	463
	11th to 20th	Day	18% 11% 26% 30% 13% 2	604
	21st to end	Day	24% 10% 24% 23% 17% 3	748
June	1st to 10th	Day	25% 15% 30% 21% 8%	870
	11th to 20th	Day	29% 14% 28% 20% 8% 1	870
	21st to end	Day	19% 15% 24% 24% 15% 3	870
July	1st to 10th	Day	19% 12% 29% 27% 11% 2	856
	11th to 20th	Day	18% 11% 31% 25% 12% 2	846
	21st to end	Day	16% 13% 27% 25% 15% 4	555
August	1st to 10th	Day	17% 10% 25% 28% 14% 5%	487
	11th to 20th	Day	15% 14% 34% 22% 11% 3	477
	21st to end	Day	19% 14% 32% 20% 11% 3	539
September	1st to 10th	Day	22% 17% 27% 21% 11% 2	490
	11th to 20th	Day	18% 15% 29% 25% 11% 2	490
	21st to end	Day	28% 21% 27% 14% 7% 2	490
October	1st to 10th	Day	22% 18% 28% 18% 9% 4	490
	11th to 20th	Day	21% 15% 29% 22% 10% 3	340
	21st to end	Day	16% 14% 30% 32% 7% 2	330
November	1st to 10th	Day	20% 11% 37% 23% 6% 3	215
	11th to 20th	Day	16% 11% 32% 28% 9% 4	180
	21st to end	Day	18% 16% 24% 26% 10% 6%	180
December	1st to 10th	Day	12% 6% 29% 30% 16% 7%	180
	11th to 20th	Day	9% 8% 30% 34% 13% 6%	180
	21st to end	Day	8% 7% 26% 37% 16% 6%	198
January	1st to 10th	Night	10% 12% 40% 31% 6% 1	1040
	11th to 20th	Night	8% 14% 41% 28% 7% 2	901
	21st to end	Night	9% 16% 43% 24% 7% 1	836
February	1st to 10th	Night	11% 14% 37% 27% 11% 1	760
	11th to 20th	Night	8% 11% 40% 31% 9% 1	744
	21st to end	Night	7% 12% 39% 28% 11% 3	628
March	1st to 10th	Night	6% 14% 40% 27% 11% 1	760
	11th to 20th	Night	6% 12% 44% 27% 10% 1	760
	21st to end	Night	8% 12% 36% 31% 11% 2	836
April	1st to 10th	Night	9% 13% 30% 35% 11% 1	760
	11th to 20th	Night	10% 10% 36% 29% 15% 1	625
	21st to end	Night	14% 8% 32% 35% 10%	421
May	1st to 10th	Night	13% 7% 24% 45% 11%	380
	11th to 20th	Night	12% 3 29% 39% 16% 1	374
	21st to end	Night	17% 8% 25% 30% 20%	411
June	1st to 10th	Night	20% 3 31% 32% 13% 1	380
	11th to 20th	Night	23% 8% 24% 32% 13% 1	380
	21st to end	Night	13% 8% 23% 34% 19% 2	380
July	1st to 10th	Night	19% 5% 19% 40% 16% 1	370
	11th to 20th	Night	15% 8% 23% 33% 21% 1	368
	21st to end	Night	9% 6% 20% 41% 22% 1	416
August	1st to 10th	Night	14% 4 15% 39% 27% 1	378
	11th to 20th	Night	14% 5% 20% 40% 19% 2	376
	21st to end	Night	16% 7% 27% 38% 11% 1	655
September	1st to 10th	Night	17% 8% 25% 37% 13% 1	760
	11th to 20th	Night	16% 7% 26% 33% 17% 1	760
	21st to end	Night	18% 13% 32% 26% 11% 1	760
October	1st to 10th	Night	16% 11% 33% 31% 9% 1	760
	11th to 20th	Night	14% 11% 39% 27% 7% 1	760
	21st to end	Night	13% 14% 42% 25% 6% 1	836
November	1st to 10th	Night	12% 13% 42% 26% 6% 1	744
	11th to 20th	Night	11% 16% 42% 26% 4 1	934
	21st to end	Night	11% 13% 47% 22% 6% 1	950
December	1st to 10th	Night	9% 12% 43% 27% 9% 1	950
	11th to 20th	Night	9% 10% 45% 27% 8% 1	1035
	21st to end	Night	6% 10% 45% 29% 9% 1	1144

Page generated at 2024-10-29 23:22:56. Version ac07

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