Olds
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Olds clear sky chart from 2005-11-06 to 2024-11-08.

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% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	105686
	Night	7% 10% 4 9% 6% 5% 5% 5% 7% 8% 35%	101976
Transparency	Day	43% 7% 16% 24% 9% 1	105431
	Night	44% 7% 15% 23% 10% 2	101877
Seeing	Day	13% 6% 25% 31% 18% 6%	15393
	Night	12% 5% 30% 36% 15% 2	24390

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	3 12% 6% 12% 6% 5% 4 4 5% 8% 34%	2219
	11th to 20th	Day	4 9% 4 11% 6% 5% 6% 6% 8% 8% 34%	2199
	21st to end	Day	5% 8% 3 9% 5% 6% 6% 3 7% 9% 39%	2794
February	1st to 10th	Day	6% 13% 5% 11% 7% 6% 6% 4 7% 8% 28%	1520
	11th to 20th	Day	5% 13% 5% 11% 8% 6% 6% 5% 7% 8% 25%	1631
	21st to end	Day	3 12% 7% 12% 6% 6% 6% 5% 7% 7% 28%	1518
March	1st to 10th	Day	3 11% 5% 13% 9% 6% 6% 4 6% 6% 29%	3138
	11th to 20th	Day	6% 10% 3 7% 4 5% 5% 4 6% 9% 41%	3444
	21st to end	Day	8% 21% 6% 12% 6% 4 4 3 5% 5% 24%	3903
April	1st to 10th	Day	8% 13% 4 10% 6% 6% 6% 5% 7% 8% 27%	2337
	11th to 20th	Day	11% 14% 5% 10% 5% 5% 5% 4 6% 8% 27%	2440
	21st to end	Day	12% 12% 4 9% 5% 4 5% 4 6% 9% 31%	2470
May	1st to 10th	Day	18% 13% 3 7% 5% 5% 4 4 5% 7% 28%	4431
	11th to 20th	Day	10% 10% 4 9% 6% 6% 6% 5% 7% 8% 30%	4694
	21st to end	Day	17% 10% 3 10% 7% 6% 6% 5% 6% 7% 24%	5161
June	1st to 10th	Day	16% 8% 3 8% 6% 5% 6% 5% 7% 8% 29%	2850
	11th to 20th	Day	18% 10% 3 8% 6% 6% 5% 5% 7% 7% 24%	2850
	21st to end	Day	8% 6% 2 7% 6% 6% 6% 5% 8% 9% 37%	2850
July	1st to 10th	Day	7% 5% 2 5% 4 4 5% 5% 6% 10% 48%	4740
	11th to 20th	Day	8% 4 1 4 4 4 5% 5% 9% 10% 46%	4740
	21st to end	Day	6% 5% 2 5% 3 4 5% 4 6% 10% 50%	5063
August	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 9% 40%	4401
	11th to 20th	Day	7% 4 2 6% 4 5% 6% 5% 8% 11% 40%	4103
	21st to end	Day	10% 5% 2 5% 4 4 4 4 7% 8% 48%	4521
September	1st to 10th	Day	11% 6% 2 5% 5% 4 4 3 6% 7% 46%	2370
	11th to 20th	Day	15% 8% 2 6% 4 3 4 3 4 7% 44%	2090
	21st to end	Day	9% 8% 3 7% 5% 4 5% 4 6% 8% 42%	2090
October	1st to 10th	Day	7% 7% 3 7% 5% 5% 6% 4 7% 9% 40%	3344
	11th to 20th	Day	7% 7% 3 8% 6% 5% 5% 5% 7% 9% 38%	2883
	21st to end	Day	7% 7% 3 9% 6% 6% 5% 3 6% 7% 41%	3101
November	1st to 10th	Day	8% 16% 5% 10% 6% 4 4 4 6% 7% 29%	1596
	11th to 20th	Day	6% 13% 5% 9% 6% 5% 4 5% 5% 6% 35%	1411
	21st to end	Day	5% 12% 4 10% 6% 5% 5% 5% 7% 8% 34%	1330
December	1st to 10th	Day	5% 12% 4 13% 7% 8% 5% 3 6% 6% 30%	1330
	11th to 20th	Day	3 10% 5% 14% 7% 5% 7% 5% 6% 9% 30%	1682
	21st to end	Day	3 9% 3 10% 6% 5% 5% 4 6% 8% 41%	2442
January	1st to 10th	Night	3 13% 6% 13% 8% 6% 6% 5% 7% 8% 26%	4726
	11th to 20th	Night	3 9% 5% 13% 7% 5% 6% 6% 7% 7% 32%	4699
	21st to end	Night	3 11% 4 11% 6% 6% 6% 5% 7% 8% 33%	4891
February	1st to 10th	Night	6% 11% 6% 13% 7% 7% 5% 3 6% 7% 28%	2660
	11th to 20th	Night	4 14% 6% 11% 6% 7% 6% 5% 6% 7% 29%	2436
	21st to end	Night	3 12% 5% 10% 6% 7% 6% 4 7% 8% 33%	1932
March	1st to 10th	Night	3 9% 4 14% 8% 8% 8% 6% 8% 7% 24%	3736
	11th to 20th	Night	6% 8% 3 8% 5% 5% 6% 5% 8% 9% 38%	3535
	21st to end	Night	7% 19% 6% 14% 8% 6% 6% 4 6% 5% 19%	3747
April	1st to 10th	Night	7% 13% 4 8% 8% 5% 6% 5% 6% 8% 29%	1843
	11th to 20th	Night	9% 14% 4 11% 7% 5% 5% 5% 6% 7% 28%	1691
	21st to end	Night	12% 10% 3 9% 6% 5% 5% 5% 7% 6% 30%	1710
May	1st to 10th	Night	21% 12% 4 8% 4 4 4 3 5% 6% 29%	2530
	11th to 20th	Night	10% 8% 3 8% 6% 5% 5% 4 8% 10% 33%	2199
	21st to end	Night	16% 11% 4 10% 7% 6% 6% 5% 7% 6% 22%	2414
June	1st to 10th	Night	17% 8% 4 7% 4 5% 6% 5% 6% 9% 29%	1330
	11th to 20th	Night	17% 9% 4 8% 6% 6% 6% 5% 6% 9% 24%	1330
	21st to end	Night	9% 6% 2 6% 6% 5% 5% 5% 8% 8% 39%	1330
July	1st to 10th	Night	7% 5% 3 8% 5% 5% 7% 4 8% 7% 41%	2220
	11th to 20th	Night	5% 4 1 4 4 5% 5% 5% 9% 10% 48%	2220
	21st to end	Night	5% 5% 2 5% 4 4 4 4 6% 9% 50%	2474
August	1st to 10th	Night	10% 6% 3 6% 5% 5% 4 4 5% 7% 44%	2529
	11th to 20th	Night	7% 5% 2 7% 5% 5% 6% 4 8% 12% 39%	2720
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 6% 8% 47%	3146
September	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 6% 8% 47%	1807
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 6% 7% 42%	2090
	21st to end	Night	10% 6% 2 6% 3 4 5% 3 7% 8% 45%	2090
October	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 4 6% 8% 45%	3631
	11th to 20th	Night	6% 7% 3 7% 5% 5% 5% 3 7% 9% 43%	4041
	21st to end	Night	5% 8% 3 7% 5% 5% 6% 5% 6% 8% 41%	4457
November	1st to 10th	Night	7% 14% 5% 9% 5% 5% 5% 4 6% 7% 33%	2624
	11th to 20th	Night	4 11% 4 10% 6% 6% 4 4 7% 8% 34%	2764
	21st to end	Night	4 11% 4 10% 6% 6% 5% 4 7% 9% 34%	2850
December	1st to 10th	Night	5% 12% 4 11% 7% 6% 5% 4 6% 7% 33%	2850
	11th to 20th	Night	2 10% 5% 12% 8% 7% 6% 5% 7% 7% 31%	3510
	21st to end	Night	3 9% 3 8% 6% 5% 5% 4 6% 7% 44%	5214

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	46% 6% 12% 22% 11% 2	2219
	11th to 20th	Day	44% 7% 10% 16% 18% 4	2220
	21st to end	Day	40% 7% 13% 31% 8% 1	2794
February	1st to 10th	Day	52% 6% 13% 18% 9% 2	1520
	11th to 20th	Day	52% 9% 14% 15% 9% 2	1640
	21st to end	Day	52% 7% 11% 18% 10% 1	1518
March	1st to 10th	Day	51% 7% 15% 16% 11%	3138
	11th to 20th	Day	36% 7% 19% 24% 14% 1	3445
	21st to end	Day	60% 7% 11% 15% 6%	3903
April	1st to 10th	Day	50% 8% 17% 16% 8%	2337
	11th to 20th	Day	53% 6% 12% 20% 9%	2440
	21st to end	Day	49% 7% 15% 21% 7% 1	2470
May	1st to 10th	Day	55% 6% 12% 23% 5%	4431
	11th to 20th	Day	46% 9% 15% 21% 9%	4698
	21st to end	Day	54% 8% 16% 16% 5% 1	5162
June	1st to 10th	Day	49% 8% 16% 20% 6% 2	2850
	11th to 20th	Day	55% 8% 14% 17% 5% 1	2850
	21st to end	Day	39% 9% 20% 24% 6% 1	2850
July	1st to 10th	Day	30% 6% 18% 29% 13% 3	4666
	11th to 20th	Day	29% 7% 20% 34% 9% 1	4659
	21st to end	Day	29% 7% 16% 29% 16% 4	4903
August	1st to 10th	Day	38% 7% 18% 30% 7%	4384
	11th to 20th	Day	35% 6% 25% 27% 7% 1	4143
	21st to end	Day	32% 6% 22% 30% 8% 1	4520
September	1st to 10th	Day	35% 6% 21% 23% 11% 4	2370
	11th to 20th	Day	40% 5% 15% 28% 11% 1	2090
	21st to end	Day	38% 6% 17% 25% 12% 3	2090
October	1st to 10th	Day	39% 5% 20% 30% 6% 1	3344
	11th to 20th	Day	41% 6% 19% 22% 11% 2	2883
	21st to end	Day	41% 5% 9% 34% 10% 1	3101
November	1st to 10th	Day	53% 7% 11% 19% 9% 2	1596
	11th to 20th	Day	47% 7% 13% 22% 10% 1	1411
	21st to end	Day	46% 8% 15% 20% 9% 2	1330
December	1st to 10th	Day	52% 7% 12% 16% 11% 2	1330
	11th to 20th	Day	48% 8% 16% 19% 6% 1	1684
	21st to end	Day	38% 6% 11% 21% 19% 5%	2442
January	1st to 10th	Night	53% 8% 12% 18% 8% 2	4726
	11th to 20th	Night	48% 6% 11% 16% 14% 5%	4740
	21st to end	Night	44% 7% 14% 24% 10% 1	4891
February	1st to 10th	Night	54% 5% 11% 18% 10% 2	2660
	11th to 20th	Night	52% 7% 12% 17% 11% 2	2437
	21st to end	Night	47% 5% 11% 22% 13% 2	1932
March	1st to 10th	Night	50% 9% 12% 20% 8% 1	3736
	11th to 20th	Night	37% 11% 20% 20% 12% 1	3535
	21st to end	Night	63% 8% 10% 13% 5% 1	3747
April	1st to 10th	Night	49% 8% 14% 19% 10% 1	1843
	11th to 20th	Night	53% 6% 12% 20% 8% 1	1691
	21st to end	Night	49% 7% 15% 21% 7% 2	1710
May	1st to 10th	Night	55% 6% 12% 21% 7%	2530
	11th to 20th	Night	41% 11% 13% 26% 9%	2199
	21st to end	Night	56% 9% 15% 15% 4 1	2414
June	1st to 10th	Night	47% 10% 15% 18% 9% 1	1330
	11th to 20th	Night	55% 8% 13% 16% 6% 2	1330
	21st to end	Night	39% 8% 20% 24% 7% 1	1330
July	1st to 10th	Night	39% 7% 15% 24% 12% 3	2185
	11th to 20th	Night	26% 8% 21% 34% 7% 4	2178
	21st to end	Night	29% 7% 15% 32% 16% 1	2396
August	1st to 10th	Night	38% 7% 15% 32% 8%	2521
	11th to 20th	Night	36% 6% 25% 27% 5% 1	2745
	21st to end	Night	33% 6% 23% 29% 8% 1	3146
September	1st to 10th	Night	34% 6% 17% 25% 14% 5%	1807
	11th to 20th	Night	39% 7% 16% 24% 10% 4	2090
	21st to end	Night	35% 6% 17% 25% 13% 3	2090
October	1st to 10th	Night	35% 4 18% 28% 13% 1	3631
	11th to 20th	Night	38% 5% 17% 28% 11% 1	4041
	21st to end	Night	40% 5% 12% 30% 11% 1	4457
November	1st to 10th	Night	49% 7% 11% 21% 10% 2	2624
	11th to 20th	Night	45% 6% 17% 19% 12% 1	2764
	21st to end	Night	44% 8% 16% 20% 9% 3	2850
December	1st to 10th	Night	49% 6% 11% 21% 10% 3	2850
	11th to 20th	Night	49% 9% 14% 21% 6% 1	3507
	21st to end	Night	36% 6% 12% 25% 15% 6%	5214

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	5% 6% 30% 31% 19% 9%	180
	11th to 20th	Day	7% 5% 37% 31% 14% 5%	180
	21st to end	Day	8% 7% 26% 34% 18% 7%	198
February	1st to 10th	Day	11% 11% 23% 34% 14% 7%	180
	11th to 20th	Day	12% 2 32% 37% 14% 4	254
	21st to end	Day	6% 5% 28% 34% 20% 6%	330
March	1st to 10th	Day	9% 6% 35% 30% 16% 5%	460
	11th to 20th	Day	9% 5% 31% 35% 13% 6%	460
	21st to end	Day	13% 7% 29% 31% 14% 5%	506
April	1st to 10th	Day	13% 9% 33% 26% 14% 4	460
	11th to 20th	Day	17% 9% 24% 29% 16% 4	452
	21st to end	Day	17% 7% 27% 30% 16% 3	460
May	1st to 10th	Day	18% 10% 22% 28% 17% 5%	525
	11th to 20th	Day	13% 7% 22% 34% 20% 5%	675
	21st to end	Day	16% 5% 17% 32% 23% 7%	734
June	1st to 10th	Day	18% 6% 25% 34% 14% 4	680
	11th to 20th	Day	20% 6% 23% 34% 13% 4	680
	21st to end	Day	9% 6% 24% 30% 22% 9%	680
July	1st to 10th	Day	12% 3 17% 34% 25% 9%	671
	11th to 20th	Day	14% 4 18% 33% 25% 7%	668
	21st to end	Day	7% 4 20% 33% 25% 10%	700
August	1st to 10th	Day	11% 3 22% 32% 22% 9%	487
	11th to 20th	Day	9% 3 22% 35% 24% 8%	477
	21st to end	Day	12% 5% 20% 33% 22% 8%	539
September	1st to 10th	Day	15% 5% 27% 28% 18% 7%	490
	11th to 20th	Day	20% 7% 21% 27% 19% 6%	490
	21st to end	Day	14% 11% 28% 28% 13% 6%	490
October	1st to 10th	Day	14% 7% 27% 30% 15% 6%	409
	11th to 20th	Day	12% 6% 32% 29% 16% 4	300
	21st to end	Day	13% 11% 33% 31% 9% 3	330
November	1st to 10th	Day	19% 5% 24% 34% 14% 4	291
	11th to 20th	Day	13% 10% 32% 31% 12% 2	219
	21st to end	Day	8% 6% 32% 28% 20% 7%	180
December	1st to 10th	Day	11% 5% 30% 32% 15% 7%	180
	11th to 20th	Day	9% 8% 39% 26% 14% 3	180
	21st to end	Day	7% 4 28% 32% 25% 4	198
January	1st to 10th	Night	9% 7% 36% 34% 13% 2	950
	11th to 20th	Night	10% 6% 38% 33% 12% 1	950
	21st to end	Night	11% 7% 34% 35% 11% 2	852
February	1st to 10th	Night	11% 8% 29% 33% 16% 3	760
	11th to 20th	Night	8% 6% 34% 36% 15% 1	744
	21st to end	Night	6% 6% 28% 35% 21% 5%	628
March	1st to 10th	Night	8% 4 32% 37% 15% 4	760
	11th to 20th	Night	8% 4 32% 39% 14% 3	760
	21st to end	Night	13% 4 28% 36% 15% 3	836
April	1st to 10th	Night	11% 7% 31% 33% 16% 2	703
	11th to 20th	Night	16% 5% 32% 36% 11% 1	563
	21st to end	Night	16% 8% 27% 36% 12% 1	570
May	1st to 10th	Night	18% 7% 28% 33% 14%	446
	11th to 20th	Night	13% 3 29% 38% 16% 1	374
	21st to end	Night	22% 4 19% 37% 17% 1	411
June	1st to 10th	Night	18% 6% 23% 37% 14% 2	380
	11th to 20th	Night	20% 4 24% 35% 16% 1	380
	21st to end	Night	12% 5% 21% 38% 23% 2	380
July	1st to 10th	Night	12% 3 14% 43% 26% 1	370
	11th to 20th	Night	13% 2 17% 47% 19% 1	368
	21st to end	Night	8% 3 18% 41% 28% 2	416
August	1st to 10th	Night	11% 3 13% 38% 34% 2	378
	11th to 20th	Night	8% 4 16% 45% 26% 1	509
	21st to end	Night	11% 4 19% 41% 25%	627
September	1st to 10th	Night	13% 3 23% 41% 18% 2	662
	11th to 20th	Night	18% 3 19% 37% 20% 3	760
	21st to end	Night	13% 4 31% 37% 14% 2	760
October	1st to 10th	Night	16% 3 28% 36% 14% 2	760
	11th to 20th	Night	12% 3 32% 37% 14% 2	760
	21st to end	Night	10% 7% 34% 36% 12%	836
November	1st to 10th	Night	15% 7% 35% 29% 12% 2	892
	11th to 20th	Night	10% 7% 41% 30% 11% 2	950
	21st to end	Night	6% 6% 39% 36% 12% 2	950
December	1st to 10th	Night	11% 6% 31% 35% 14% 2	950
	11th to 20th	Night	9% 6% 37% 35% 12% 2	950
	21st to end	Night	11% 4 33% 35% 14% 2	1045

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